This thesis is a numerical study of turbulent thermal convection driven by free-surface evaporation in water pools. The studied physical phenomenon is closely related to the flow occurring in the early stages of a spent-fuel pool (SFP) loss-of-cooling accident (LOCA), such as that which occurred at Fukushima 2011. Here, the important interdependent physical phenomena are free-surface evaporation and turbulent thermal convection.

First, a configuration similar to turbulent Rayleigh-Bénard Convection (RBC) is investigated, but with a free-slip upper boundary condition approximating a free surface. Fixed temperature, boundary conditions are applied above and below, and the role of the free-slip and non-Oberbeck-Boussinesq effects on the mean flow properties are investigated. The free-slip is shown to play an important role on heat transfer in the domain and on the homogeneity of the thermal boundary layer heights.

Secondly, a representative evaporative heat flux is then prescribed uniformly as the thermal boundary condition above. Time-averaged properties of the flow, are shown to be influenced by the presence of the free surface and a novel Rayleigh number scaling of the Nusselt number is found. The latter shows a remarkably similar exponent to that of turbulent RBC, but where an increased prefactor accounts for the shear-free boundary.

Finally, a novel dynamic thermal boundary condition based on evaporative and convective heat losses at a free surface is developed and implemented and the role of aspect ratio on the large-scale circulation (LSC) state is investigated. The LSC is shown to switch from a stable single-roll, to a dual-roll state, changing the temperature and velocity fields at the free surface. However, no discernible impact on the evaporation rate is found. The results of this thesis are useful both academically and in industry with respect to the modelling of the early stages of an SFP-LOCA with system codes.

Jury members :

• Prof. Miltiadis Papalexandris (UCLouvain), supervisor
• Prof. Laurent Delannay (UCLouvain), chairperson
• Prof. Juray De Wilde (UCLouvain), secretary
• Prof. Laurence Rongy (ULB, Belgium)
• Dr. Vincent Deledicque (Bel V, Belgium)
• Dr. Holger Grosshans (National Metrology Institute, Germany)

Pay attention :

The public defense of William Hay scheduled for Friday 26 February at 16:30 will take place in the form of a video conference Teams

Friction stir : much more than welding by Aude Simar (Professor at UCLouvain)

Friction stir welding is now well known as a solid-state welding process in particular for the assembly of aluminium alloys. We will quickly discuss the advantages of this welding process and this will lead us to the conclusion that this process can be exploited to manufacture new materials or improve their properties exploiting the large plastic deformation involved in this process. In that perspective, we have improved by a factor 100 the fatigue life of 3D printed aluminium alloys, developed new self-healing aluminium based composites or developed new NiTi reinforced aluminium that exploit the shape memory effect to deviate cracks and enhance toughness. A whole new way of thinking about material design freed from the limitations of traditional manufacturing….

Link to teams

Laser powder bed fusion (LPBF) AlSi10Mg is a promising material for lightweight structural applications in the aerospace sector. Its fine microstructure grants high mechanical strength. However, there is still a gap in the understanding of the correlation between microstructure and mechanical behaviour. Besides, the critical fatigue issue still represents a significant hurdle. Despite the relative flexibility of the LPBF additive manufacturing process, there is a limitation in the possibility of tailoring parameters to obtain a satisfactory combination of porosity and surface roughness for adequate fatigue resistance. From this quandary arises the interest for post-treatments to overcome this limitation.

First, a comprehensive microstructural characterisation was carried out. It started by looking at the as built state, including the build platform temperature and loading direction aspects. A detailed 3D microstructural analysis involving focused ion beam/scanning electron microscopy tomography was performed to describe the connectivity and size of the Si-rich eutectic network and link it to the strength and fracture strain. An analytical model was developed to exploit these microstructural features and predict the strength of the material.

The fracture and fatigue of LPBF AlSi10Mg were studied under as built and three post-processing conditions, stress relieve heat treatment, hot isostatic pressing and friction stir processing (FSP). FSP proved to be a viable solution to improve the fatigue behaviour. Indeed, thanks to this post-process that reduces overall porosity and eliminates critical defects while keeping a satisfactory fine microstructure and static mechanical behaviour, the fatigue resistance of the material was significantly enhanced. In contrast, the other studied post-processes did not have a positive impact on fatigue.

Jury members :

• Prof. Aude Simar (UCLouvain), supervisor
• Prof. Renaud Ronsse (UCLouvain), chairperson
• Prof. Pascal Jacques (UCLouvain), secretary
• Prof. Brecht Van Hooreweder (KULeuven, Belgium)
• Prof. Anne Marie Habraken (ULiège, Belgium)
• Asst. Prof. Manas Upadhyay (Ecole Polytechnique, France)
• Asst. Prof. Marie-Noëlle Avettand-Fénoël (Université Lille 1, France)

Pay attention :

The public defense of Juan Guillermo Santos Macias scheduled for Thursday 22 April at 5:00 p.m will take place in the form of a video conference Teams

This lecture delivers an overview of the research activities carried out at the von Karman Institute that investigate some of the most complex internal flows found in rotating machinery and that contribute to the development of future gas turbine technologies.

In the first part of the seminar, we will discuss how to redesign compact high-pressure turbines to control leakage and cooling flows using state-of-the-art optimization techniques and novel blade parametrizations. The lecture will show how we proved the virtual performance gains of multiple optimum blade geometries by engine-representative experiments in a short-duration turbine facility that makes use of a rainbow rotor and hundreds of high-frequency sensors and probes.
In the second part of the talk, we will look into one of the largest research projects of the von Karman Institute that explores the aerodynamics of transonic low-pressure turbines for the next-generation geared turbofan engines. The research focuses on the unsteady interactions of cavity purge and leakage flows with the high-speed primary turbine flow by time-resolved flow measurements in two world-class turbine rigs: a transonic low-Reynolds linear cascade, recently revamped for quasi-3D flow measurements of turbine airfoils subject to secondary-air injections and incoming periodic wakes; and the VKI rotating turbine rig equipped with a high-speed one-meter-large low-pressure turbine stage. Join the seminar

   Dr. Sergio Lavagnoli is currently an Associate Professor in the Turbomachinery and Propulsion department of the von Karman Institute for Fluid Dynamics (Rhode-Saint-Genese, Belgium). He received his PhD in Applied Sciences from the Polytechnic University of Valencia (Spain) in 2012 on a study devoted to the aerodynamics and heat transfer of a transonic high-pressure turbine stage with a multi-splitter turbine vane frame.

Professor Lavagnoli has more than 10 years of experience on experimental and numerical aerothermal studies on gas turbine engine turbomachinery. The main focus of his research includes fundamental studies on the aerodynamics and heat transfer of jet-engine turbines, turbomachinery optimization and the development of instrumentation and data processing techniques.

After his Engineering Degree at the University of Liège in Belgium in 1992, Jean-François Remacle obtained in 1997 a Ph.D. from the same University. He then spent two years at the Ecole Polytechnique de Montréal as a post-doctoral fellow of Prof. F. Trochu, followed by three years at Rensselaer Polytechnic Institute in the research team of Prof. M. Shephard (one year as research associate followed by two years as research assistant professor). It was during his stay at Rensselaer that Pr. Remacle started to work closely with Mark Shephard on mesh generation. Pr. Shephard's seminal work on mesh generation is one of the most important contributions ever. It was also during that stay that Pr. Remacle started the development of Gmsh, the open source mesh generator. After these five years in Northern America, Jean-François Remacle joined the Université catholique de Louvain in 2002 as an assistant Professor. He then became Associate Professor in 2005 and Full Professor in 2012. In the following years of his return to Europe, Pr. Remacle dedicated a large part of his research to mesh generation.

Participate in the seminar via Teams

Pour l’obtention du grade de Docteur en sciences de l’ingénieur et technologie

Boundary layer transition from laminar to turbulent generates high levels of shear stresses and heat transfer rates, influencing the overall efficiency of the aircraft engine. This is especially detrimental to the performance of the high-pressure turbine, which is subjected to elevated levels of flow turbulence and temperature gradients from the upstream combustor, and to strong stream-wise pressure gradients. Hence, a more complete understanding of the transition phenomenon and combustor turbulence would help in its prediction for the design and analysis of more efficient blades and vanes.

Our main goal is to improve the limited knowledge on the boundary layer transition physics in the high-pressure turbine. Since turbine experimental testing in facilities is usually on the lower range of turbulence intensity, how does increasing the cascade inlet turbulence to the levels found downstream of a combustor chamber affect the boundary layer state and heat transfer? And are the thermal effects negligible for bypass transition? Our research focus is in understanding the weight and consequence of high free-stream turbulence and gas-to-wall temperature ratio on boundary layer transition, and to extend our high-pressure turbine heat transfer database to account also for these effects. Our experimental boundary layer studies are based on time-resolved wall heat flux measurements performed in the Isentropic Compression Tube (CT-2) facility at the von Karman Institute. This facility simulates the flow conditions found in an aircraft engine turbine in terms of free-stream turbulence, Mach and Reynolds numbers, and gas-to-wall temperature ratios (TR), which are independently variable. The test model is a linear five vane cascade of the VKI LS89 highly loaded turbine guide vane profile.

We first developed a new turbulence grid to generate turbulence levels in excess of 10%, for more engine-representative inlet flow turbulence. The resulting passive square/diamond bar grid induces turbulence intensities between 10-26% and integral length scales in the order of 1-2 cm.

The TR survey shows that there is a small effect on the stability of the boundary layer. Increasing the flow temperature led to a later/longer transition, but only when the pressure gradients were mild. A clear effect on the transition length was observed at a free-stream turbulence of 6%.

The high levels of turbulence intensity led to strong changes in boundary layer transition and heat transfer when comparing to a natural turbulence case. Between turbulence levels, however, the pressure gradients mostly drive transition, i.e., delaying transition onset with acceleration and triggering it with deceleration. Increasing the turbulence intensity could shift transition for a fully subsonic velocity distribution, but for transonic, steeper pressure gradients, the effect was limited to a reduction of a shock-induced separation bubble, and slightly earlier transition onsets, still suppressed by strong accelerations. Varying the facility Reynolds number had a small coupling with the Mach number, but it was still clear the overall increase of heat flux, and the earlier transition.

Implicit LES in collaboration with Cenaero led to the high-fidelity simulation of the LS89 cascade. By means of their numerical code Argo and cluster Zenobe, we simulated an important test case (MUR235), with both bypass transition, relaminarization, and shock-induced transition. While the heat transfer profile could not be perfectly matched, we could observe a high sensitivity to a numerical parameter, the artificial viscosity (AV). Depending on the level of AV, which could not be decoupled from the shock and boundary layer, an almost perfect match is obtained for MUR235 up to the turbulent boundary layer, which remained under-predicted. However, increasing the resolution, consequently, reducing the AV, led to a very distinct transition behavior. The resulting heat transfer profile indicates a laminar boundary layer up to the shock, which is instead in line with the present measurements.

In sum, experimental and numerical endeavors imply that boundary layer transition is even more sensitive to the environment than expected, with special emphasis on the pressure gradients.

Jury members :

• Prof. Vincent Legat (UCLouvain), supervisor
• Prof. Tony Arts (UCLouvain), supervisor
• Prof. Laurent Delannay (UCLouvain), chairperson
• Prof. Francesco Contino (UCLouvain), secretary
• Prof. Sergio Lavagnoli (von Karman Institut, Belgium)
• Prof. Koen Hillewaert (Université de Liège, Belgium)

Pay attention :

The public defense of Tania Sofia Cação Ferreira scheduled for Thursday 29 April at 5:00 p.m will take place in the form of a video conference Teams

Pour l’obtention du grade de Docteur en sciences de l’ingénieur et technologie

A constant growing use of titanium alloys results from their excellent properties including good corrosion resistance, specific strength and biocompatibility. However, their extensive use is partly hindered by a lack of ductility, strain hardening, and fracture toughness.

Recently, several β-metastable titanium alloys were designed to simultaneously activate both transformation-induced plasticity and twinning-induced plasticity effects, resulting in significant improvement of both their strain hardening capacity and resistance to plastic localization. However, their fracture properties have not been investigated yet.

The present thesis aims at uncovering the fracture process of these alloys. An ultra-large fracture resistance resulting from a high resistance to damage nucleation is observed in several β-metastable Ti alloys. An unexpected fracture phenomenology involving adiabatic shear banding occurs under quasi-static loading, which is strongly dependent on the geometry of the tensile specimen. Their excellent ductility is also kept after short ageing treatments.

A significant temperature rise up to the melting temperature of the alloys is estimated using the fusible coating method and is associated with a very large crack propagation speed, measured by high speed imaging. The evolution of the microstructure during quasi-static straining and after fracture is characterized by transmission electron microscopy. A pre-necking localization of the deformation is also detected by digital image correlation analysis.

Jury members :

• Prof. Pascal Jacques (UCLouvain), supervisor
• Prof. Laurent Delannay (UCLouvain), chairperson
• Prof. Hosni Idrissi (UCLouvain), secretary
• Prof. Thomas Pardoen (UCLouvain)
• Prof. David Embury (Mc Master Univ., Canada)
• Prof. Patricia Verleysen (UGent, Belgium)
• Prof. Roland Logé (EPFL, Switzerland)

Pay attention :

The public defense of Laurine Choisez scheduled for Friday 30 April at 4:30 p.m will take place in the form of a video conference Teams

Jury members :

Prof. Alain Holeyman (UCLouvain), supervisor
Prof. Pierre Latteur (UCLouvain), supervisor
Prof. Hervé Jeanmart (UCLouvain), chairperson
Prof. Hadrien Rattez (UCLouvain), secretary
Prof. Mounir Bouassida (Université de Tunis El Manar, ENIT, Tunisie)
Prof. Benoit Pardoen (Université de Lyon / LTDS, ENTPE, France)
Prof. Richard Merifield (Université de Newcastle, Australie)

Numerical simulation is a powerful tool to analyze complex physical phenomena for scientific analysis and engineering design. Mesh generation is an essential step of numerical methods, providing a subdivision of the physical domain in question to a finite number of simple elements.

Quadrilateral and hexahedral meshes offer certain advantages compared to triangular and tetrahedral meshes, such as reduced number of elements and alignment with problem-specific directions. Nevertheless, while there exist mature methods to generate the latter, there are no conclusive algorithmic solutions for the former.

The objective of this thesis is to provide a framework for the robust and efficient generation of high-quality quadrilateral and hexahedral-dominant meshes. A hybrid approach is followed by borrowing elements from engineering techniques for mesh generation, graph theory, and the computer graphics community. Cross-fields are used to place points across the domain optimally. A two-step method using local mesh modifications is developed for surface meshing that enables the robust generation of meshes with cross-field aligned triangles. The output cross-field aligned triangular mesh can be converted to an all-quadrilateral mesh in an indirect fashion by merging pairs of triangles using a novel bipartite labeling scheme. Finally, the quality of output quadrilateral meshes can be further optimized by locally remeshing with topological patterns. The same indirect approach is followed for volume meshing. A complete pipeline for hexahedral-dominant meshing is developed, and the use of integrable frame-fields is investigated.

The developed pipelines are used to produce meshes on a large number of models with diverse characteristics in order to test the robustness limits. The algorithms are efficient since they are mainly based on local operations. Overall, the approach presented offers a pragmatic solution for the mesh generation of “real-life”, complex models.

Jury members :

• Prof. Jean-François Remacle (UCLouvain), supervisor
• Prof. Thomas Pardoen (UCLouvain), chairperson
• Prof. Vincent Legat (UCLouvain), secretary
• Dr. Jonathan Lambrechts (UCLouvain)
• Prof. Koen Hillewaert (Université de Liège, Belgium)
• Dr. Franck Ledoux (CEA, France)
• Prof. Cecil Armstrong (Queen’s University, N. Ireland)
• Dr. Gaëtan Compère (Siemens, Belgium)

Pay attention :

The public defense of Christos Georgiadis scheduled for Wednesday 26 May at 4:30 p.m will take place in the form of a video conference Teams

In recent years, a controversy has developed as to whether, within a few decades, renewable energies could meet all the world energy needs, without jeopardising economic growth. To shed a new light on this debate, a new methodology has been developed in this thesis to estimate global wind and solar potentials and the associated Energy Return on Investment (EROI). Additionally, the obtained results have been coupled with a macroeconomic model to assess the feasibility and the economic impacts of the energy transition.

The model shows that, although having a twice higher global potential, solar technologies present lower EROIs than wind technologies. The global worldwide potentials obtained lie in the lower ranges of the estimations found in the literature, while for the European countries, the total potential is only equivalent to the current final energy consumption of this region. This maximum potential can only be achieved if all of the theoretically available areas are covered with wind farms and solar fields, including areas with low energy profitability, especially for solar power plants. The actually achievable potential will depend partly on the sustainable minimum EROI; in other words, on the maximum price, in terms of energy and capital costs, at which we can afford to produce our energy in the future.

When results of the energy model are coupled with a macroeconomic model, simulations show that in a business-as-usual context, a complete energy transition on a global scale is unachievable before the end of the century. The reason lies in the increasing capital needs of the energy sector as the share of renewable energies progresses, which slows, if not stops, economic growth and the energy transition itself. Provided that (i) energy demand is kept under control at its current level, (ii) a sufficient rate of capital growth is sustained (above its historical level), and (iii) substantial progress is made in terms of energy efficiency, a complete transition could be achieved by 2070. However, this strategy requires a significant increase in the savings rate with a negative impact on public and private consumption, which would end up stagnating at the end of the transition.

Jury members :

• Prof. Hervé Jeanmart (UCLouvain), supervisor
• Prof. Thomas Pardoen (UCLouvain), chairperson
• Prof. Emmanuel De Jaeger (UCLouvain), secretary
• Prof. Jean-François Fagnart (Université Saint-Louis, Belgium)
• Dr. Iñigo Cappelán-Pérez (Universidad de Valladoid, Spain)

Pay attention :

The public defense of Elise Dupont scheduled for Tuesday 01 June at 4:00 p.m will take place in the form of a video conference Teams

Conducted disturbances in the frequency range 2-150 kHz have gained more interest over the last few years due to the evolution of the power grid. The traditional low frequency harmonics are indeed replaced by emissions in this frequency range due to the technological evolution towards self-commutating topologies. Furthermore, Power Line Communication is one of the chosen options as a means of communication for smart metering infrastructures. This technology uses the power network and works in the same frequency range, i.e. 2-150 kHz. At the same time, the standardization on this issue is still incomplete.

This thesis brings a contribution towards a better understanding of this kind of electromagnetic compatibility issue. This work adopts a theoretical approach for the development of the required models of the disturbing devices and the grid.

The two main categories of disturbing devices have been modelled. First, self-commutated inverters, such as those met in solar panels or in wind turbines, are considered. Both single-phase and three-phase configurations are investigated. The other category concerns rectifiers with Active Power Factor Correction as in Compact Fluorescent Lamps or in some electric vehicle chargers. The obtained models offer an interesting compromise between accuracy and simplicity.

The low voltage grid model consists of several elements in series where each element is in turn represented by three chain matrices for the positive, negative and zero sequence components.

Finally, the thesis provides an accurate method to study theoretically the propagation of one or several disturbances in that frequency range.

Jury members :

• Prof. Emmanuel De Jaeger (UCLouvain), supervisor
• Prof. Laurent Delannay (UCLouvain), chairperson
• Prof. Marc Bekemans (UCLouvain), secretary
• Prof. Véronique Moeyaert (UMons, Belgium)
• Prof. Jos Knockaert (UGent, Belgium)
• Prof. Sarah Rönnberg (LULEA University of Technology, Sweden)

L’humain exploite des ressources pour répondre à ses besoins énergétiques. Depuis la nuit des temps, du bois a été consommé pour la cuisson et le chauffage. Avec la révolution industrielle, les besoins en énergie ont entamé une forte croissance. Ce sont les énergies fossiles, stockées dans le sol depuis des millions d’années, qui ont comblé cette demande. Le bois et les énergies fossiles ont l’atout majeur d’être facilement stockable, au contraire du vent, du soleil et des rivières. Or, la transition énergétique que nous entamons requiert de substituer les énergies fossiles (stockable) par des énergies renouvelables (intermittentes). Comment va-t-on assurer la disponibilité de l’énergie quand nous en aurons besoin ?

Cette thèse s’intéresse à l’intégration des énergies renouvelables intermittentes et au rôle des technologies de stockage durant la transition énergétique. Pour ce faire, un modèle optimisant la transition a été développé. Il représente l’ensemble du système énergétique d’un pays, c’est-à-dire toute la chaine depuis l’importation des ressources ou leur exploitation locale jusqu’à la consommation d’énergie sous forme d’électricité, de chaleur ou pour la mobilité. Cette chaîne intègre la conversion et le stockage des ressources énergétiques.

Ce modèle, appelé EnergyScope, permet de générer des trajectoires d’un système énergétique d’aujourd’hui jusqu’à une société neutre en émissions à l’horizon 2050. Son application au cas de la Belgique permet de comparer différents scénarios et d’identifier les tendances qui nous attendent pour les décennies à venir.

Jury members :

• Prof. Hervé Jeanmart (UCLouvain), supervisor
• Prof. Laurent Delannay (UCLouvain), chairperson
• Prof. Emmanuel De Jaeger (UCLouvain), secretary
• Prof. François Maréchal (EPFL, Switzerland)
• Prof. Erik Delarue (KULeuven, Belgium)
• Prof. Stefan Pfenninger (Delft, Netherlands)

Pay attention :

The public defense of Gauthier Limpens scheduled for Friday 18 June at 4:30 p.m will take place in the form of a video conference Teams

The long-standing desire for a profound understanding of the surrounding physical phenomena has led to numerous scientific breakthroughs, which are mirrored in the development of formalism and the means to predict the behavior of these abstract systems. In the language of mathematical physics, these phenomenons are described through the lenses of a particular entity: the partial differential equations (PDEs), which aid the comprehension of an abstract physical system’s life cycle through time and space.

The numerical methods represent a driving force in finding the solution of the specific PDE, requiring discretization of both the equations and the geometrical model on which the computation is performed, and are used in many fields: aeronautics, automotive design, meteorology, fluid mechanics, soil mechanics, biomechanics, medical imaging, civil engineering, electrical engineering, and electronics.

The subject of this thesis is precisely targeting the challenging issue of discretization of geometrical models, i.e., robust and high-quality block-structured quadrilateral mesh generation. In order to reach this goal, the rigorous mathematical background served as the foundation and motivation for developing the corresponding methodology. The exploration of Ginzburg-Landau PDE and its related theory, previously known in the field of superconductors, as well as the properties of an auxiliary object cross-field hand-in-hand with the use of a quad layout concept, turned out to be very fruitful idea for this matter.

Jury members :

• Prof. Jean-François Remacle (UCLouvain), supervisor
• Prof. Thomas Pardoen (UCLouvain), chairperson
• Dr. Jonathan Lambrechts (UCLouvain), secretary
• Dr. Maxence Reberol (UCLouvain)
• Prof. Christophe Geuzaine (ULiège, Belgium)
• Dr. Franck Ledoux (Alternative Energies and Atomic Energy Commission, France)
• Dr. Nicolas Ray (Institut national de recherche en sciences et technologies du numérique, France)

Pay attention :

The public defense of Jovana Jezdimirovic scheduled for Monday 24 August at 4:00 p.m will also take place in the form of a video conference Teams

sphincter muscle, which, if damaged, can cause urinary incontinence. Facial muscles also share such similarities and must be replaced after an accident or injury. Although these muscles do not play a vital role in the body, they remain extremely important for patients’ quality of life, for example a well-functioning sphincter muscle is critical in order to avoid unpleasant side effects such as needing to wear diapers. The parallels between muscle types could allow the development of universal electromechanical multifunctional actuators. Within the new «Center for Artificial Muscles», EPFL, in cooperation with its partners in heart surgery - University of Bern and Reconstructive Medicine - University of Zürich, aims to become the world’s leading reference for the development and clinical transfer of a brand new technological approach for artificial muscles in the human body.

Biography: Yves Perriard obtained his Master in ‘Microengineering’ from EPFL in 1989 and his PhD form the Electrical Department in 1992. He became cofounder of the company Micro-Beam SA and had the lead of the company until 1998 doing special electric drives. In 1999 he joined EPFL as Senior Lecturer and in 2003 he was appointed Titular Professor and leader of the Integrated Actuators Laboratory. In 2009 he is also appointed Vice-Director of the Microengineering Institute EPFL Neuchâtel. Senior member IEEE and Member EPE, he is also vice-president of the EPE (European Power Electronics) society board in Brussels.

Yves Perriard is interested in innovating, analyzing and creating new actuators associated with their electronic devices.  The multi-disciplinary work of his research makes him strongly in contact with industries in Switzerland and abroad. Yves Perriard has published over 180 papers, 5 patents and is co-author of one book. He is associate editor of several journals. Teacher at the Bachelor and Master level, he received twice the best teacher award of the Engineering Faculty in 2005 and 2007. More information can be found on the Integrated Actuators Laboratory web site http://lai.epfl.ch. In 2018, he launched a brand new center at EPFL on artificial muscles thanks to a donation of the Werner Siemens Foundation.

Bibliography :

• Feasibility of a Dielectric Elastomer Augmented Aorta, Morgan Almanza,* Francesco Clavica, Jonathan Chavanne, David Moser, Dominik Obrist, Thierry Carrel, Yoan Civet, and Yves Perriard, Advanced Science. 2021-01-25. Vol. Volume 8, num. Issue 6. DOI : 10.1002/advs.202001974.
• Untethered Feel‐Through Haptics Using 18‐µm Thick Dielectric Elastomer Actuators, X. Ji; X. Liu; V. Cacucciolo; Y. R. C. Civet; A. El Haitami et al. Advanced Functional Materials. 2020-10-07. Vol. 30, num. 41, p. 1-10, 2006639. DOI : 10.1002/adfm.202006639.

While playing on an acoustic piano, a pianist feels an essential sensory information called the touch. Along with the sound, these two feedbacks give the musician greater control and expressivity with the instrument. Touch mainly results from the highly dynamic response of the key-to-string transmission called piano action. Present-day digital pianos offer the possibility to nuance the sound with a quite impressive quality. However, the touch feedback is not nearly as good as that of an acoustic piano keyboard.

This work first presents a multibody model that allows analyzing the grand piano action behavior and understanding its functioning. In addition, experimental validation have been successfully achieved, both in kinematics and in dynamics.

Secondly, a piano key prototype actuated by a custom-made linear actuator is proposed to enhance the touch of digital pianos. A multibody model computes the action dynamics in real-time, in such way that the actuator provides the same haptic feeling at the key. Rendering a grand piano action model within the haptic key prototype shows promising results and demonstrates the feasibility of our approach.

This thesis highlights the interest of the multibody approach for demystifying the piano action behaviour, and for enhancing the touch of digital pianos.  

Jury members :

• Prof. Paul Fisette (UCLouvain), supervisor
• Prof. Anne-Emmanuelle Ceulemans (UCLouvain), supervisor
• Prof. Thomas Pardoen (UCLouvain), chairperson
• Prof. Bruno Dehez (UCLouvain), secretary
• Prof. Arend Schwab (Delft University of Technology, Netherlands)
• Prof. Yves Perriard (Ecole Polytechnique fédérale de Lausanne, Switzerland)
• Prof. Philippe Lefèvre (UCLouvain)

Fe-based alloys are of increasing interest for the use as bioresorbable materials. Their mechanical properties are adequate for the use as stents but they present too slow degradation rates. Alloying with Mn allows to achieve excellent work-hardening, further increasing the mechanical properties, and renders the Fe alloy more susceptible to corrosion. Nevertheless, high amounts of insoluble hydroxides are formed during Fe-Mn corrosion, which increase the local pH, favouring the deposition of salts coming from the blood environment. Altogether, these layers hinder the oxygen diffusion from the electrolyte towards the metal surface, decreasing the corrosion rate with time.

The present thesis aims at increasing the corrosion susceptibility of Fe-Mn-C Twinning Induced Plasticity (TWIP) steels in Simulated Body Fluid (SBF). Local acidification can lead to an enhanced dissolution of the corrosion layers, achieving increased corrosion rates. A novel way to acidify the local environment is explored in the present work: the release of hydrogen previously charged within the steel. It is found that H charging achieves only slight increase in corrosion susceptibility due to the low hydrogen presence not allowing to completely counter the complex interactions with the electrolyte. Its influence on the corrosion properties is compared to PLA-coating and Cu-coating on TWIP steel. Both techniques have proven to effectively increase the corrosion properties of Fe-based alloys. The influence of hydrogen on the corrosion kinetics is similar to PLA-coating but smaller than Cu-coating. Cu-coated and H-charged samples present similar corrosion products morphologies, whereas the PLA-coated samples present higher iron hydroxides presence, leading to heavy red/orange corrosion products.

Jury members :

• Prof. Pascal Jacques (UCLouvain), supervisor
• Prof. Laurent Delannay (UCLouvain), chairperson
• Dr. Quentin Van Overmeerre (UCLouvain), secretary
• Prof. Dominique Lison (UCLouvain)
• Prof. Xavier Feaugas (Université de La Rochelle, France)
• Dr. Xavier Vanden Eynde (CRM Group, Belgium)
• Dr. Dimitri Mercier (Chimie Paris Tech, France)

Pay attention :

The public defense of Sarah Reuter scheduled for Wednesday 29 September at 4:30 p.m will take place in the form of a video conference Teams

The cornerstone of machine learning is the availability of data: it is not difficult to build extremely sophisticated nonlinear models of the relation between a high number of features and output(s), but the lack of hypotheses on the underlying phenomenon has to be compensated by a lot of data (and sometimes really a lot of…). In some domains it is easy to collect huge amounts of data, in other domains it is far more difficult (patient records for example). The difficulty is not to build a model that fits well data, but to build a model that does not overfit the data especially when data are scarse, which is unavoidable in high-dimensional spaces.

This talk will present the main lines of the state-of-the-art in machine learning, including but not limited to deep learning, the main challenges, and opportunities for research purposes and applications.

To answer these questions, we propose a global stability analysis on solid cases (uncontrolled) and partially porous cases (controlled) in order to study the global modes of the resulting flows and to determine the ability of porous layers to delay flow bifurcations. This stability analysis will be performed on 2D and 3D cases, for the first flow bifurcations. An optimization strategy will also be proposed to identify relevant positions of the porous patches at the solid surface.

The numerical solution of high-frequency Helmholtz problems by discretization methods such as the finite element method is a big challenge. Indeed, obtaining high-fidelity solutions requires to assemble and solve extremely large linear systems, whose size increases more than linearly with frequency. This can quickly lead to intractable computational costs both in terms of the assembly and the solution of the resulting linear systems. To overcome these difficulties, we implement an efficient quadrature approach applied to the high-order finite element method as well as domain decomposition methods with high-order transmission conditions, in two- and three dimensions, on high-performance computers. To improve the convergence rate of domain decomposition methods, we generalize a family of sweeping preconditioners for the domain decomposition methods, where sweeps can be done in several directions on block-type partitions. In order to apply our algorithms to practical cases that require solutions for large number of frequencies or a large number of right-hand sides, we also propose improved parallelization strategies that maintain the fast rate of convergence while maximizing the usage of computer resources.

Jury members :

• Prof. Jean-François Remacle (UCLouvain), supervisor
• Prof. Christophe Geuzaine (ULiège), supervisor
• Prof. Renaud Ronsse (UCLouvain), chairperson
• Prof. Philippe Chatelain (UCLouvain), secretary
• Dr. Jonathan Lambrechtst (UCLouvain)
• Prof. Xavier Antoine (IECL, France)
• Dr. Eric Bréchet (ULiège)
• Dr. Axel Modave (Ensta, Paris, France)

Pay attention :

The public defense of Ruiyang Dai scheduled for Wednesday 17 November at 4:15 p.m will take place in the form of a video conference

Indeed swimming organisms at large have refined their senses, morphologies, gaits and mechanical properties to effectively propel and maneuver in a variety of unsteady flow conditions. The understanding of new design paradigms that exploit flow induced mechanical instabilities for propulsion or energy harvesting demands robust and accurate flow structure interaction numerical models. In this context, we develop a novel two dimensional algorithm that combines a Vortex Particle-Mesh (VPM) method and a Multi-Body System (MBS) solver for the simulation of passive and actuated structures in fluids.

Jury members :

Prof. Philippe Chatelain (UCLouvain), supervisor
Prof. Renaud Ronsse (UCLouvain), supervisor
Prof. Laurent Delannay (UCLouvain), chairperson
Prof. Paul Fisette (UCLouvain)
Prof. Chloé Mimeau (CNAM, France)
Prof. Mattia Gazzola (UIUC, USA)

Will also take place in the form of a video conference

Flows involving the transport of a dispersed solid phase by a carrier fluid are encountered in many environmental phenomena and industrial applications. Fluidized beds are now used in a wide variety of processes in the petrochemical and pharmaceutical sectors, in biomass conversion or in the food industry, among others. Those systems are characterized by a very large range of length and time scales, leading to a multiscale modeling strategy. At the smallest scale, particle-resolved direct numerical simulation (PR-DNS) is a first-principles based approach, providing the complete details of the flow. With growing computational resources, PR-DNS has become a tool of choice to develop closure models for the mass, momentum and energy transfer terms that cannot be captured in large-scale Euler-Lagrange and Euler-Euler approaches.

In this thesis, we first develop and validate a direct-forcing immersed boundary method to perform particle-resolved simulations of two- and three-dimensional fluid-particle flows. The numerical method is subsequently applied to quantify the interfacial momentum and heat transfer terms in random particle arrays. While current drag laws only provide the mean value of the fluid-particle force, we propose a microstructure-based model to estimate the distribution of the hydrodynamic force using a few quantities characterizing the local organization of the solid phase. The inhomogeneity of the thermal problem and the impact of thermal saturation on the distribution of the fluid-particle heat flux are also discussed. Then, we perform a detailed comparison of the dynamics of small-scale fluidized beds in different regimes. In liquid-solid fluidization, the small inertia of the particles leads to a homogeneous suspension and the motion of the particles is mainly driven by anisotropic self-diffusion. In gas-solid fluidization, the higher inertia of the solid particles leads to the emergence of heterogeneities in the bed (bubbles and clusters) and to a strong vertical oscillatory motion. Finally, we investigate the influence of different physical and computational parameters on the bed dynamics.

Jury members :

• Prof.  Juray DE WILDE (UCLouvain), supervisor
• Prof. Grégoire WINCKELMANS (UCLouvain), supervisor
• Prof. Olivier SIMONIN (IMFT)
• Prof. Simon SCHNEIDERBAUER (JKU)
• Prof. Yann BARTOSIEWICZ (UCLouvain)
• Prof. Laurent BRICTEUX (UMons)

You can also connect via Teams

Essential to space missions involving an atmospheric entry, the thermal protection system (TPS) shields the spacecraft and its payload from the severe aerothermal loads. Low-density carbon/phenolic composite materials have gained renewed interest to serve as ablative thermal protection materials (TPMs). These materials can accommodate the high heating rates and heat loads encountered during the atmospheric entry, at hypersonic velocities, by absorbing part of the incoming heat through physico-chemical transformations. One of the main endothermic processes is the pyrolysis of the resin compound, whereby volatile products are released, leaving a carbonaceous residue is left on the fibers.

Whereas new experimental data have already been published to characterize the decomposition of these low-density carbon/phenolic materials, they are yet to be exploited for the inversion of physico-chemical models. In addition, the issue of uncertainty quantification, required to assess the reliability of the numerical model and the physico-chemical models, is yet to be addressed. Therefore, the overarching objective of this thesis is to contribute to the development of an uncertainty-quantified numerical modeling of the ablation of new porous composite materials and to the analysis of the impact of uncertainty on TPS design. To that aim, we first address the development and the uncertainty characterization of physico-chemical models for resin pyrolysis on the basis of new experimental data relevant to the pyrolytic decomposition of the phenolic resin used in carbon/phenolic composite TPMs. Then, we analyze the impact of the uncertainty in the physico-chemical models on the numerical modeling of ablation of TPS by means of non-intrusive stochastic methods.

The central contribution of this thesis is to infer from these new experimental data an uncertainty-quantified pyrolysis model. We adopt a Bayesian probabilistic approach to account for uncertainties in the model identification. We use an approximate likelihood function involving a weighted distance between the model predictions and the time-dependent experimental data. To sample from the posterior, we use gradient-informed Markov chain Monte Carlo methods with an adaptive selection of the numerical parameters. We develop a versatile code for performing uncertainty characterization using Bayesian inference tools on engineering problems in which the proposed methods are implemented. To select the decomposition mechanisms to be represented in the pyrolysis model, we proceed by progressively increasing the complexity of the pyrolysis model until a satisfactory fit to the data is ultimately obtained. To improve the computational time, we derive a fast semi-analytical solution for the resin pyrolysis using multicomponent parallel reactions both for the case of a constant temperature and the case of a linear heating rate. The pyrolysis model thus obtained involves six reactions and has 48 parameters.

A second contribution is the assessment of the impact of uncertainties on the material response of an ablating TPS relevant to in-flight performance prediction. Using the six-reaction pyrolysis model, we demonstrate its use in a numerical simulation of heat shield surface recession in a Martian entry. We provide probabilistic projections of the recession of the surface, the production of gaseous species at the surface, and the temperature.

In addition to the aforementioned contributions, we also provide three supplementary pieces of research. For the first one, we contribute to the development of a model for representing the process of ablation from resin pyrolysis to char ablation in a unified flow-material approach where the Volume-Averaged Navier-Stokes equations are solved. This model is implemented in the high-fidelity numerical code Argo from the research center Cenaero and verified by a code-to-code comparison. The second one pertains to the development of an uncertainty-quantified pyrolysis model including competitive mechanisms for the pyrolytic decomposition of the PICA material. Finally, the third one concerns the calibration of material properties and environmental conditions in a Bayesian inference framework using post-flight data of the Mars Science Laboratory mission.

Jury members :

• Prof. Philippe CHATELAIN (UCLouvain, Belgium), supervisor
• Prof. Arnst MAARTEN (Université de Liège, Belgium), supervisor
• Prof. Thierry MAGIN (Université de Liège, Belgium), supervisor
• Prof. Miltiadis PAPALEXANDRIS (UCLouvain, Belgium)
• Prof. Vincent TERRAPON (Université de Liège, Belgium)
• Dr. Jean LACHAUD (Université de Bordeaux, France)
• Dr. Pietro CONGEDO (Inria Saclay île-de-France, France)

Accessible via Teams

La technologie des PCB felixibles permet de développer de nouveaux types de bobinages qui améliorent les performances des moteurs électriques. On peut en eet remplacer le bobinage laire habituel par un circuit imprimé, sur lequel il est possible de dessiner des pistes de cuivre aux formes très variées, ce qui amène de nouveaux degrés de liberté exploitables pour l’optimisation des moteurs.

Ce travail se concentre plus précisément sur le cas des petits moteurs DC synchrones à aimants permanents avec entrefer lisse, pour lesquels les PCB exibles sont particulièrement bien adaptés. Le choix d’utiliser des aimants se justie par le développement des terres rares qui permettent maintenant d’obtenir une grande densité d’énergie. Le choix d’une topologie avec un entrefer lisse procure de nombreux avantages et est guidé par le fait que, d’une part elle laisse la place à un arrangement des conducteurs complètement libre, et que d’autre part elle permet la réduction des pertes fer, du couple de dentures, des vibrations ou encore du bruit, grâce à l’absence de dents ferromagnétiques.

Bien que les bobinages sur PCB aient démontré leur ecacité à faible vitesse, on y observe rapidement l’apparition de courants induits lorsque la vitesse du moteur augmente. Car à même section de conducteur, les pistes de cuivre imprimées sont plus larges que le l que l’on retrouve dans des bobinages standards et par conséquent de plus grandes surfaces conductrices sont exposées perpendiculairement au champ magnétique des aimants en rotation.

L’objectif principal de la thèse est donc de modéliser les pertes par courants induits pour les estimer et réduire leur impact lors de la conception et de l’optimisation des moteurs.

La première partie de la thèse concerne la modélisation de ces pertes. Un modèle de départ utilisant des éléments nis 3D et, s’appuyant sur une formulation de la magnétodynamique en potentiel vecteur, est présenté. Partant de ce modèle de référence, dès lors qu’on connait l’expression du champ magnétique induit par les aimants permanents, on montre qu’il est possible d’estimer les pertes par courants induits à l’aide d’un modèle 2D FEM de façon beaucoup plus rapide et moins couteuse en temps de calcul. Cette réduction du coût de calcul permet entre autresde modéliser un bobinage de moteur au complet et d’y observer l’évolution des courants induits. Ce modèle, en plus d’être rapide et précis, a la particularité intéressante de prendre aussi en compte la forme et la topologie des conducteurs. Par la suite un modèle analytique est également proposé an de disposer d’un outil capable d’estimer les pertes par courants induits en un temps encore plus réduit. Ce modèle analytique nous donne la possibilité de prendre en compte ces pertes dans le cadre d’une procédure d’optimisation qui demanderait un très grand nombre d’évaluations. Afin de valider les modèles proposés, un banc d’essai expérimental a été mis en place.

La deuxième partie de la thèse met en oeuvre les diérents modèles créés afin d’étudier, d’une part l’impact de ces pertes sur le design optimal d’un moteur en fonction de son point de fonctionnement donné et, d’autre part la pertinence d’utiliser des modèles éléments nis pour l’optimisation d’un moteur. En plus de conrmer que les pertes par courants induits sont essentielles à prendre en compte dans le cas de bobinages PCB, un premier résultat montre que la principale variable d’ajustement lorsque l’on souhaite changer le point de fonctionnement du moteur, est la largeur des pistes conductrices. Une seconde observation indique qu’il est possible de tendre vers une conception presque optimale uniquement à l’aide de modèles analytiques.

La troisième partie de la thèse propose une stratégie permettant de limiter les pertes par courants induits. Une simple diminution de la largeur des conducteurs n’est pas susant car elle va de paire avec une augmentation du nombre de spires du bobinage. Or dans ce cas, la tension d’alimentation étant limitée par l’électronique de puissance, cela impliquerait de mettre des spires en parallèle au détriment d’éventuels courants de recirculation. La solution suggérée pour résoudre ce problème est de dessiner des coupures isolantes dans les pistes de cuivre de la façon la plus adéquate possible. Cela revient à réaliser des parallélisations à une échelle plus locale, sans impacter la tension d’alimentation du moteur. Ce travail a mis en évidence les congurations optimales pour ces coupures et a montré qu’elles l’étaient pour toute une gamme de points de fonctionnement.

Jury members :

• Prof. Bruno Dehez (UCLouvain, Belgique), supervisor
• Prof. Aude Simar (UCLouvain, Belgique), chairperson
• Dr. Francois Henrotte (UCLouvain, Belgique)
• Dr. François Baudart (UCLouvain, Belgique)
• Prof. Elena Lomonova (TU/e, EPE group, Netherlands)
• Prof. Yves Perriard (EPFL, LAI, Switzerland)

For the degree of Doctor of Engineering Sciences and Technology

This thesis aims at curvilinear mesh generation and adaptation, we start from summary ideally the research project as a simple yet fundamental question: assume a unit square $$\Omega = \{(x^1,x^2) \in [0,1] \times [0,1]\}$$ and a smooth function $f(x^1,x^2)$ defined on the square, and consider a mesh $\mathcal T$ made of $P^2$ triangles that exactly covers the square, how can we compute the mesh $\mathcal T$ that minimizes the interpolation error $\| f - \Pi f\|_\Omega$. Here, $\Pi$ is the nodal interpolation of $f$ on the mesh \cite{ern}.

We state the problem as to build a unit curvilinear mesh, i.e. build a mesh with unit edge lengths that are possibly curvilinear. We solve the problem in three stages of increasing complexity:

1. input a unit square and a metric field $g(x,y)$, to build a unit curvilinear mesh that is possibly anisotropic;
2. input a function $f(x,y)$, to build an anisotropic curvilinear mesh that minimizes the approximation error;
3. input a high order finite element solution, to build an anisotropic curvilinear adapted mesh.

We propose \emph{a new framework} of curvilinear mesh generation and adaptation: metric field construction, generation of points (point sampling on the boundary and point sampling in the domain), straight-sided mesh generation and adaptation (triangulation and straight-sided edges swap), curvilinear mesh generation and adaptation (straight-sided edges curving, curvilinear edges swap, and Curvilinear Small Polygon Reconnection).

A unit curvilinear mesh containing only valid ``Geodesic Delaunay triangles'' is obtained this way.

In this approach, the curvature is not only used to match curved boundaries but also to capture features of the interpolated solutions, and it results in meshes that would not have been achievable by simply curving \emph{a posteriori} a straight-sided mesh. A number of application examples are presented in order to demonstrate the capabilities of the mesh adaptation procedure.

Jury members :

• Prof. Jean-François REMACLE (UCLouvain, Belgium), supervisor
• Prof. Renaud RONSSE (UCLouvai, Belgium), chairperson
• Dr. Jonathan Lambrecht, (UCLouvain, Belgium)
• Prof. Vincent Legat (UCLouvain, Belgium)
• Dr. Thomas TOULORGE (Cenaero, Belgium)
• Prof. Thierry COUPEZ (Mines-ParisTch, France)

Joining via Teams : https://teams.microsoft.com/l/meetup-join/19%3ameeting_MGJhOWE1MmYtMDdlMC00ZjljLTg2NmMtMjI1NTc2MTYyZWM1%40thread.v2/0?context=%7b%22Tid%22%3a%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2c%22Oid%22%3a%229ef2ead8-17d6-4db7-af70-e05edd8a39c5%22%7d

The present lecture will briefly present the basics of the method and the way the results can be processed and analysed using particule tracking, microstructurally faithful modelling and/or Digital Volume correlation. The examples will be selected in everyday-life : mechanics of cables, setting of plaster and in situ indentation of plaster boards, electrical cycling of batteries...

This thesis consists of a detailed study of spray combustion of diesel and biodiesel fuels. Our study is focused on the complex physical and chemical phenomena that take place in such flows and consists of three parts.

In the first part, we investigate atomization and droplet breakup of a non-reactive fuel spray via Large-Eddy Simulations (LES). To this end, we compare three popular droplet-breakup models, the Taylor Analogy Breakup (TAB), Reitz-Diwakar and Pilch-Erdman models. Further, we propose a modification of the original TAB model and assess its predictive capacity. According to our numerical tests, the proposed modification leads to improved accuracy in the computation of important properties of the spray, such as the liquid- and vapor-penetration distance.

In the second part, we present a numerical study of n-dodecane spray flames via LES. With regard to combustion modelling and turbulence-chemistry interaction, we employ the Flamelet-Generated Manifolds (FGM), which is based on tabulated chemistry. Herein, we propose a novel approach for the coupling of the energy equation with the FGM database that offers considerable computational savings. The efficiency of this approach is assessed via comparisons with experimental data and earlier numerical results for n-dodecane spray flames.

In the last part of the thesis, we present an LES study of spray combustion of Karanja Oil Methyl Ester. For computational efficiency, the chemical kinetics is represented by the combustion mechanism of a surrogate fuel that is a blend of n-dodecane (64.32%) and methyl butanoate (35.68%). First, we examine the influence of the initial oxygen concentration level on the spray ignition and the flame topology. Further, we compare the combustion processes of the biodiesel surrogate with the corresponding diesel surrogate (n-dodecane). Finally, we assess the impact of the thermophysical properties of the biodiesel on the evolution of the spray and the overall combustion process.

Jury members :

• Prof. Miltiadis PAPALEXANDRIS (UCLouvain, Belgium), supervisor
• Dr. Holger GROSSHANS (PTB, Germany), supervisor
• Prof. Eric DELEERSNIJDER (UCLouvain, Belgium), chairperson
• Prof. Francesco Contino (UCLouvain, Belgium)
• Dr. Véronique DIAS (UCLouvain, Belgium)
• Dr. Christos VARSAKELIS (Janssen Pharmaceutical, Belgium)
• Dr. Kai Moshammer (PTB, Germany)

Visio conference link

The first part of the presentation is devoted to the effect of electrostatic forces on the dispersion of small inertial particles, with the same charge, carried by a homogeneous isotropic turbulent flow for very dilute configurations. This phenomenon is analyzed by means of direct numerical simulations (DNS) coupled with Lagrangian tracking of electrically charged particles. The simulation results show that the kinetic energy, self-dispersion and segregation of the particles decrease with increasing electrical charges. Statistical analysis of the simulation results in the framework of the joint fluid-particle PDF approach shows that the decrease in kinetic energy and self-dispersion of charged particles is due to a decorrelation effect between the turbulent velocities of the fluid and the particles by electrostatic forces. Such an effect can be modelled by introducing a Coulomb collision cross section by analogy with the elastic collision effect on particle dispersion in turbulent flows.

The second part of the presentation is devoted to the statistical modelling of the mean electric charge transport with triboelectric effects in mono-dispersed gas-particle flows for kinetic and collisional regimes. The kinetic theory of granular flows is used to derive the transport equations for the mean particle electric charge and for the secondorder moments: charge-velocity correlations and charge variance. The collision terms in these equations are closed by assuming that the electrostatic interaction does not modify the collision dynamics and without presuming explicitly the form of the dependence of the joint charge-velocity PDF on the particle electric charge. A linear model for the mean electric charge conditioned by the instantaneous particle velocity is proposed to account for the charge–velocity correlations in the computation of the collision terms. First, a gradient dispersion model for the charge-velocity correlations is derived from the corresponding transport equation by using simplifying hypotheses. The gradient dispersion model is tested in a periodic box with non-uniform initial mean charge distribution. The results show that the dispersion phenomenon has two contributions: a kinetic contribution due to the electric charge transport by the random motion of particles and a collisional contribution due to the electric charge transfer during particle–particle collisions. Another phenomenon that contributes to the mean electric charge transport is a triboelectrical current density due to the tribocharging effect by particle–particle collisions in the presence of a global electric field. Second, a full second-moment transport equation model is tested in the periodic box with nonuniform initial mean charge distribution. The results show that this model is able to capture some important mechanism that are neglected in the gradient dispersion modelling approach and, in particular, allows to account for the coupling with the charge variance production and dissipation.

In recent years, bioelectrochemical systems (BES), such as microbial fuel cells (MFC), have been explored for their benefits in the treatment of complex wastewater.

Textile wastewater mixtures are far from ideal electrolytes for an electrochemical process, generating bioincubations on electrodes and separators, which greatly affect cell performance. There is an extensive literature on the methodology of modification and preparation of nanofiltration membranes with antifouling properties for membrane tegnology, which, added to the potential advantages of these membranes (oxygen retention and lower electrical resistance compared to ion selective membranes), generates a great expectation for the use of this type of separators never before used in bioelectrochemical systems.

The objective of this work is to explore the modification processes of nanofiltration membranes to provide them with antifouling properties and efficient separators in microbial fuel cells and in a new gereration of microbial (osmotic) nanofiltration fuel cells, for the treatment of textile wastewater.

The bio-inspired modification method used polydopamine and photocatalysts as antifouling agents. Tests showed that membranes modified with poldopamine and ZnO or with a mixture of catalysts (TiO2:ZnO) acquired antibacterial and antifouling activity. Thus, the modification process was applied in low-cost membranes as separators of MFCs, which showed significant improvement in COD and color removal and electricity production in MFCs. In order to improve the visible light activation efficiency of the catalyst and the antifouling properties of the membranes, a new catalyst (ZnO Er/Al) was synthesized. The new catalyst was used in the production of nanofiltration microbial fuel cells with antifouling membranes, which showed both the efficiency of these membranes to maintain a constant water flux during long osmotic periods of evaluation and excellent antifouling properties. These results and the wide variety of available nanofiltration membranes show a promising future of research.

Jury members :

• Prof. Patricia Luis Alconero (UCLouvain, Belgium), supervisor
• Prof. Hervé Jeanmart (UCLouvain, Belgium), chairperson
• Prof. Laurent Francis (UCLouvain, Belgium)
• Prof. Denis Dochain (UCLouvain, Belgium)
• Prof. Anthony Szymczyck (Université de Rennes 1, France)
• Prof. Korneel Rabaey (Ghent University, Belgium)
• Prof. Pablo Bonilla (Central University of Ecuador)

Visio conference link

The high-quality two-dimensional (2D) crystals possess remarkable mechanical behaviour which offers exciting opportunities for new material selection and design, like the combination of extremely high in-plane stiffness and bending flexibility. For this reason, the nanomechanical testing of 2D layers and their 3D heterostructures is vital for proving their functionality in different applications. In this work, different nanomechanical testing including membrane deflection, nanoindentation and tensile have been performed with various techniques such as atomic force microscopy, nanoindentation and lab-on-chip developed in UCLouvain, respectively. By using these methods, the elastic and plastic behaviour of graphene as well as its effect on the mechanical response of copper thin film have been investigated. For each technique, some challenges are required to be faced and some uncertainties needed to be considered in order to extract the mechanical response precisely. Membrane deflection on single and bilayer graphene has been performed in order to extract Young’s modulus and fracture strength of these layers by considering the uncertainties and errors that can occur regarding the device calibration and experimental procedure. The effect of CVD-graphene on the plastic behaviour of Cu thin film in two different configurations has been investigated by nanoindentation in two different modes which are complementary to each other limitations. In this configuration, graphene acted as a perfect barrier against the movement and propagation of dislocations underneath the indent. In the last part, lab-on-chip (LOC) technique has been used to evaluate the effect of graphene on the fracture and creep behaviour of thin film of copper. Because of the limitations and challenges that are faced, there are no useful experimental results extracted in this section. However, a well-defined, adopted process for Cu/Gr specimens with Ni actuators has been proposed and the solutions for most of the challenges in each step are provided which make it easy for future investigations.

Jury members :

• Prof. Thomas Pardoen (UCLouvain, Belgium), supervisor
• Prof. Jean-Pierre Raskin (UCLouvain, Belgium), supervisor
• Prof. Hervé Jeanmart (UCLouvain, Belgium), chairperson
• Prof. Bernard Nysten (UCLouvain, Belgium)
• Prof. Jean-Christophe Charlier (UCLouvain, Belgium)
• Prof. Joris Everaerts (Materials Engineering, Belgium)
• Dr. Marc Verdier (SIMaP, France)

Visio conference link

Natural gas and biogas are both consisting of large amounts of methane and are predominantly used for energetic usage, while around 5 % are used for chemical conversion in chemical industry. The methane usage will continue for many years to come, while both conversions take place with non-optimal efficiencies. One approach to overcome these low efficiencies is to use piston engines as chemical reactors for a combined production of work, heat, and useful chemicals like syngas (H₂/CO) or acetylene. Such a polygeneration process is quite fuel rich, and thus, due to low flame speeds, a kinetically controlled homogeneous charge compression ignition process (HCCI) is preferable. This leads to the problem that methane is quite inert and measures are needed to ignite it after compression. High initial temperatures, high compression ratios, or different additives can help to overcome the inertness and can lead to ignition in such engines. These systems were analyzed with respect to the chemical kinetics, the thermodynamics, and the exergo-economics; in addition concepts for energy recuperation and product separation were developed and analyzed. In total, it is found from theory and from experiment that the combined process is in many cases preferable in comparison to separate processes for energy conversion and chemical conversion, but some challenges remain, like the relatively high amounts of additives needed for ignition. The concept can be expanded further towards using the piston-cylinder system as a compressor to convert mechanical energy in endothermal reactions to chemical energy for chemical energy storage, as will be explained. Results and ideas from several cooperation partners within the DFG research unit 1993 ‘Multifunctional conversion of species and energy’ will be presented.

Biography

Dr. Burak Atakan is currently a full professor for thermodynamics and Chair of Engineering Thermodynamics, department of Mechanical and Process Engineering at University of Duisburg-Essen. He received his Diploma in chemistry from University of Heidelberg and PhD in 1992 also from University of Heidelberg. Before he joined University of Duisburg-Essen, he was a research scientist and at DLR and Bielefeld University, and obtained his Habilitation in physical chemistry in 2000. Prof. Atakan received Benningsen Foerder Prize of the State of North Rhine-Westphalia in 1997. He is a Fellow of the Combustion Institute. He was in the Editorial board of the Energy section of Applied Sciences and the Editorial board of Open Journal of Thermodynamics.

Aluminium alloys are widely used as structural materials in transportation, space and construction. Despite the excellent combination of lightweight with sufficient strength, to remain competitive on the market, several properties of Al alloys should be further enhanced, such as strength properties and damage tolerance. One way to improve the strength of Al alloys is to combine them with reinforcements, thus processing Aluminium matrix composites (AMCs). These materials present several advantages compared to Al alloys, such as higher strength, elevated temperature resistance and lower thermal expansion coefficient. In addition, to improve damage tolerance of Al alloys and AMCs, Friction Stir Processing (FSP) can be used. However, the classical approach of damage prevention is not the only solution to improve damage tolerance and meet materials sustainability requirements. Instead, damage management approach can be used to achieve alloys longevity, among which self-healing strategies are good approaches. In the present study, a new healable Al alloy/composite presenting healing behaviour was produced by FSP. A new Programmed Damage and Repair (PDR) healing concept was proposed. In this concept, the damage provoked by the load appears on sacrificial particles. When the selected healing heat treatment is applied, healing occurs using the matrix atoms as a healing source. Healing was demonstrated using in-situ heating under nanoholotomography and TEM.

Jury members :

• Prof. Aude Simar (UCLouvain, Belgium), supervisor
• Prof. Hosni Idrissi (UCLouvain, Belgium), supervisor
• Prof. Hervé Jeanmart (UCLouvain, Belgium), chairperson
• Prof. Pascal Jacques (UCLouvain, Belgium), secretary
• Dr. Eric Maire (INSA Lyon, France)
• Prof. Sybrand van der Zwaag (TU Delft, the Netherlands)
• Dr. Willimas Lefevre (Université de Rouen, France)

Visio conférence link

The present thesis investigates the influence of 7XXX aluminium alloys microstructure on damage mechanisms. 7XXX alloys are widely used as structural materials due to their high strength and low density. However, strength was obtained at the expense of ductility, which is a limiting factor for forming applications.

It was revealed in the literature that the microstructure of 7XXX alloys is affecting damage initiation, growth and coalescence. This correlation between microstructural features and damage mechanisms opens the way for mechanical performances optimization by microstructural changes. Indeed, the 7XXX alloys microstructure is complex and its modification by thermomechanical and heat treatments is not obvious.

Friction Stir Processing (FSP) was selected for refining the 7XXX alloys microstructure. Obtaining FSPed material in full strength condition was a first achievement presented in this work. This specific FSPed material has a significantly 180% higher ductility compared to the standard base alloy at equivalent 500 MPa tensile strength, which is a proof that ductility can be improved in 7XXX alloys. In situ X-ray tomography is used for revealing the changes in fracture mechanisms after FSP.

However, despite higher ductility, the FSPed 7XXX alloys do not show higher crack propagation resistance, which is an unexpected decoupling of the ductility versus toughness. Investigations were pursued for understanding better the damage mechanisms and the crack propagation behaviour of the manufactured 7XXX alloys microstructures.

The understanding of damage sequence in 7XXX aluminium alloys is then transposed to a numerical model that simulates intrinsic components of the real microstructure in order to predict the material failure. This model offers an outlook for designing new 7XXX microstructures, reaching high strength, ductility and toughness simultaneously.

Jury members :

• Prof. Aude SIMAR (UCLouvain, Belgium), supervisor
• Prof. Renaud RONSSE (UCLouvain, Belgium), chairperson
• Prof. Thomas PARDOEN (UCLouvain, Belgium)
• Prof. Laurent DELANNAY (UCLouvain, Belgium)
• Dr. Florant HANNARD (UCLouvain, Belgium)
• Dr. Sylvain DANCETTE (INSA Lyon, France)
• Prof. Ludovic NOELS (ULiège, Belgium)
• Dr. Jean-Christophe EHRSTRÖM (Constellium, France)

Visio conference link

The control and characterization of the fracture behavior of thin films and 2D materials, in the era of continuous device miniaturization, are of paramount importance for the design and integrity assessment of many coatings and microelectronics devices towards more reliable devices. However, the available test methods suffer from many limitations mainly when the film rests on a substrate due to different constraints that are difficult to deconvolute and or with the introduction of an initial sharp precrack in freestanding configurations. In this context, the objective of this research is to develop a robust fracture on-chip technique for freestanding thin films and 2D materials. This crack-on-chip method consists of actuator beams produced by lithography undergoing large internal stress attached to a notched specimen beam. Both actuators and specimens are deposited on top of a Si substrate. The etching of a part of this substrate induces the release of the test structure, with the actuators then contracting and pulling on the test specimen. If the applied displacement is large enough, a crack initiates at the notch root and propagates. The design has been selected such as to involve a decrease of the crack driving force after some amount of crack growth leading to crack arrest. avoiding the problem of notch opening of the precrack. The technique can also be used to investigate the environmentally-assisted cracking in thin-film materials. The fracture toughness of SiO₂ (142 nm), SiN (50 nm), Al₂O₃ (190 nm), and CVD-grown monolayer graphene were extracted. It was found that Al₂O₃ films are more prone to subcritical aging compared to SiN, while simultaneously exhibiting larger resistance to environmental cracking than thermally-grown SiO₂ films. For single-layer graphene, fracture strain, Young’s modulus, strength, and Weibull modulus were determined with, for the first time, statistically representative data.  

Jury members :

• Prof. Thomas Pardoen (UCLouvain, Belgium), supervisor
• Prof. Jean-Pierre Raskin (UCLouvain, Belgium), supervisor
• Prof. Hervé Jeanmart (UCLouvain, Belgium), chairperson
• Prof. Hosni Idrissi (UCLouvain)
• Prof. Ingrid De Wolf (KULeuven, Belgium)
• Prof. Benoit Merle (University of Erlangen-Nürnberg, Allemagne)
• Prof. Ludovic Noels (Uliège, Belgium)

Visio conference link

High entropy alloys (HEAs) have attracted a lot of attention in recent years, with the promise of new alloy systems with outstanding (combinations of) structural (and functional) properties. However, in-depth investigations of HEAs mechanical properties in direct comparison to conventional alloys have been seldom reported. The goal of this thesis was to characterize two so-called Cantor-based HEAs, CoCrFeMnNi and CoCrNi alloys, and to compare them to reference conventional alloys in the framework of structural materials for cryogenic applications, namely stainless steels (type 304L and 316L), iron-nickel alloys (Invar and Fe9Ni), and a high Mn TWIP steel (Fe-22Mn-0.5C). To this end, the selected alloys were tested at room and cryogenic temperatures, and thoroughly characterized in terms of microstructure, hardening and fracture properties. The essential work of fracture (EWF) method is well suited to quantify the fracture resistance of ductile thin sheets and was extensively used in this work. One of the outcomes of the thesis is an improved EWF methodology that minimizes the required material while keeping the same statistical error on the extracted EWF value. Among the seven investigated materials, HEAs showed excellent tensile and fracture properties both at 293 K and 77 K. However, stainless steels keep exhibiting even better performances in terms of strength, ductility, and fracture toughness.

Jury members :

• Prof. Pascal Jacques (UCLouvain, Belgium), supervisor
• Prof. Thomas Pardoen (UCLouvain, Belgium), supervisor
• Prof. Sandra Soares-Frazao (UCLouvain, Belgium), chairperson
• Prof. Aude Simar (UCLouvain, Belgium)
• Prof. Stéphane Godet (ULB, Belgium)
• Dr. Jean-Denis Mithieux (Aperam, France)
• Prof. Dierk Raabe (Max-Planck Institute, Allemagne)
• Prof. Guillaume Laplanche (Ruhr-Universität Bochum, Allemagne)
   

Visio conference link

For practical applications we commonly hear about the potential benefits of seeking inspiration from nature, but there are also some inherent risks within this approach. This presentation will consider some examples of how bioinspired design can be effective, and how it can lead to problematic engineering solutions.

We will also consider how computational engineering methods can be applied to biological locomotion systems, not for bioinspired design, but simply to gain a deeper understanding of the natural world.

Ben Parslew’s academic background is in aerospace engineering, fluid dynamics and biomechanics. His research lies at the interface of engineering and biology, with particular interests in animal locomotion, unmanned aerial vehicles, aerodynamics, robotics and computer animation. Ben is a senior lecturer in Aerospace Engineering at University of Manchester in UK, and also a visiting lecturer at Chulalongkorn University in Thailand.

Semi-crystalline polymers exhibit performances that are highly dependent on their micro-structure as induced by the thermo-mechanical processes they are subjected to. In this thesis we developed a multiscale modeling and simulation framework able to predict the thermo-mechanical response of semi-crystalline polymers including crystallization and porosity evolution, with an application to additive manufacturing by selective laser sintering.

Firstly, an enhanced phase field model was developed for the numerical simulation of crystallization in semi-crystalline polymers. The model is numerically implemented using the finite difference method so that 2D and 3D simulation results are presented and compared to experimental data, illustrating the quantitative adequacy of the predictions with experimental evidence.

Secondly full-field micromechanical simulations were conducted on the micro-structures generated by the enhanced phase field model in order to predict the effective mechanical properties. An FFT solver was used to determine the thermo-mechanical properties for a range of crystallinity ratios. Validation against experimental data and comparison with simpler models was done.

Thirdly, we developed the constitutive laws enabling the prediction of the thermo-viscoelastic-viscoplastic behavior of semi-crystalline polymers. The crystalline lamellae follow an orthotropic elasto-viscoplastic model based on the activation of slip systems, while the amorphous phase is viscoelastic. Some material parameters were identified directly while others were reverse engineered from experimental measurements.

Finally, a mesoscale model was proposed for the density evolution of an initially low density polymer grain powder which becomes compacted after sintering. The approach is based on a generalized self-consistent model, the analogy between linear elasticity and Newtonian fluid and the mass conservation equation. All the models have been implemented in a research version of the Digimat software.

Jury members :

• Prof. Issam Doghri (UCLouvain, Belgium), supervisor
• Prof. Laurent Adam (Hexagon, Belgium), supervisor
• Prof. Sandra Soares-Frazao(UCLouvain, Belgium), chairperson
• Prof. Evelyne Van Ruymbeke (UCLouvain, Belgium)
• Prof. Stéphane Bordas (Université du Luxembourg)
• Prof. Hans Van Dommelen (T.U. Eindhoven, Netherlands)
• Prof. Wim Van Paepegem (Ghent University, Belgium)

This talk will present modeling approaches for problems where the dissipative (far-from equilibrium) processes operating at the microscope are tightly coupled with the response of the macro scale, thereby prohibiting asymptotic homogenization and scale separation to be valid. An alternative will be presented based on alternative, non-extensive entropy measures from statistical thermodynamics, and the macroscopic structures of the dissipative processes will be presented. Applications of these principles to clean energy problems will be presented, including the control of fracture networks and fault reactivation in geothermal energy production as well as storage of energy residues including nuclear waste, hydrogen and CO2.

Short Bio: Manolis Veveakis is currently an Associate Professor of the Department of Civil and Environmental Engineering, Duke University. He earned a Ph.D. in 2010 from the Department of Mechanics of the National Technical University of Athens, Greece. Before joining Duke University, he was a Senior Lecturer at UNSW's School of Petroleum Engineering since 2014 and a Research Scientist in CSIRO's Division of Earth Sciences and Resource Engineering before that. Veveakis holds a Diploma (BSc+MEng) in Applied Mathematics and Physics (MEng in Materials Engineering), an MSc in Applied Mechanics and a PhD in Geomechanics.

In this talk, I will promote a new holistic view on manipulation semantics, which combines the perception and execution of manipulation actions in one unique framework, the so-called “Semantic Event Chain” (SEC). The SEC concept is an implicit spatio-temporal formulation that encodes actions by coupling the observed effect with the exhibited roles of manipulated objects. In the first part of the talk, I will explain how such semantic action encoding can allow robots to link continuous visual sensory signals (e.g., image sequences) to their symbolic descriptions (e.g., action primitives). To highlight the scalability of manipulation semantics, I will introduce various applications of SECs in learning object affordances, coupling language and vision, and memorizing episodic experiences. In the second part of my talk, I will talk about employing scene semantics to solve the domain translation problems in the context of autonomous driving.

Bio: 

Eren Aksoy is an Associate Professor (Docent) at Halmstad University in Sweden. He obtained his Ph.D. degree in computer science from the University of Göttingen, Germany, in 2012. During his Ph.D. study, he invented the concept of Semantic Event Chains to encode, learn, and execute human manipulation actions in the context of robot imitation learning. His framework has been used as a technical robot perception-action interface in many EU projects (e.g., IntellACT, Xperience, ACAT). Before moving to Sweden, he spent 3 years as a postdoctoral research fellow at the Karlsruhe Institute of Technology in the H2T group of Prof. Dr. Tamim Asfour. He has also been a visiting scholar at Volvo GTT and Zenseact AB in Sweden, working on AI-based perception algorithms for autonomous vehicles. He serves as an Associate Editor in different high-ranking robotics journals and conferences (RA-L, IROS, Humanoids, etc.). His research interests include action semantics, computer vision, AI, and cognitive robotics. He has been actively working on creating the semantic representation of visual experiences to achieve a better environment and action understanding for autonomous systems such as robots and unmanned vehicles. He is the main coordinator of a Horizon Europe project ROADVIEW focusing on robust automated driving in extreme weather.

Burning fossil fuels for energy production has caused a significant increase in CO₂ emissions. Excessive emission over the past decades is leading to catastrophic problems for the environment related to global warming. One of the prevailing solutions for the reduction of CO₂ emissions from the power plants is CO₂ capture and storage/utilization technologies.

In this thesis, CO₂ is considered a source of carbon, a valuable compound that is worth recovering as a high-purity bicarbonate salt (NaHCO₃), which can be used in the industry to try to close the carbon cycle. The proposed process includes two main steps, membrane-based absorption, and membrane distillation crystallization. In the first step, membrane-based absorption is used as an alternative to the conventional CO₂ capture process. A green solvent, i.e. amino acids, is used to convert CO₂ into NaHCO₃ using a membrane contactor as a non-selective barrier that provides the contacting surface for the gas and liquid phases.In the next step, NaHCO₃ is crystallized using a osmotic membrane distillation crystallization (OMDC) process. In the OMDC, the driving force is a difference in the water activity of the osmotic and feed solutions, which results in the evaporation of water from the feed into the osmotic solution.

Jury members :

• Prof. P. Luis Alconero (UCLouvain, Belgium), supervisor
• Prof. R. Ronsse (UCLouvain, Belgium), chairperson
• Prof. Tom Lessens (UCLouvain, Belgium)
• Prof. Eric Favre (Lorraine University, France)
• Prof. Francesco Macedonio (ITM, CNR, Italy)
• Dr. Karine Cavalier (Solvay Co., Belgium)

Visio conference link : https://teams.microsoft.com/l/meetup-join/19%3ameeting_MTkwNzM2ZjctNDVhMC00Y2FiLWFiMTctMzMxNzYzNDlhNGJj%40thread.v2/0?context=%7B%22Tid%22%3A%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2C%22Oid%22%3A%2287448214-f9f4-4c61-9ab7-ba22ac9a3424%22%2C%22IsBroadcastMeeting%22%3Atrue%2C%22role%22%3A%22a%22%7D&btype=a&role=a

Birds have always been a source of inspiration for humans. From the record distances crossed by the bar-tailed godwit during its migrations, to swifts staying aloft continuously for up to ten months, they are capable of achievements that artificial devices are still far from reproducing. We still have a lot to learn from the flight of birds, and the unveiling of the mechanisms behind their efficiency could open the way to new levels of performances for our man-made air vehicles.

While many works have relied on observations and experimental measurements conducted on birds and have led us to a certain knowledge of their flight mechanisms, the present work builds upon the idea that reproducing bird flight in simulation can shed light on what makes them so efficient. Indeed, plain mimicry of the natural flight of birds does little toward the better understanding of its underlying principles whereas the numerical reproduction of the broad range of phenomena involved allows us to test various hypotheses.

In this thesis, we report on the development of a model for bird flapping flight. This model includes a representation of the wing skeleton and the main flight feathers, controllers aimed at the stabilization of flight and a faithful modeling of the wake behind a bird.

The model is applied to the study of the dynamics of a bird in controlled flight, the analysis of its wake and of the interactions between two birds flying in formation. In the results, we present predictions regarding the distribution of aerodynamic forces and the contributions to the flight power. We also analyze the structure of a bird wake, verifying hypotheses concerning the positioning of a bird flying behind another, and we simulate the formation flight of two birds, exploring the control strategies that stabilize the follower, and how its position affects the reduction in its flight power.

Jury members :

• Prof. Philippe Chatelain (UCLouvain), supervisor
• Prof. Renaud Ronsse (UCLouvain), supervisor
• Prof. Eric Deleersnijder (UCLouvain), chairperson
• Prof. Grégoire Winckelmans (UCLouvain), secretary
• Prof. Grigorios Dimitriadis (ULiège)
• Prof. Ben Parslew (Manchester University, UK)

Visio conference link

Every year, migratory birds liven the sky up by aligning in arrows and drawing impressive V-shapes. The energetic efficiency of this flying technique is explained by the existence of a wake in a region behind every individual and that each can perceive. Just like birds, airplanes also leave a wake consisting of two parallel vortices made visible in the sky by the condensation trails of the engines. Just like birds, are airplanes also able to take advantage of the wake of an aircraft in front of them? This thesis is devoted to bringing some elements of answer to that question by focusing on the concept of extended formation flight characterized by a several tens of wingspan distance between the leader and the follower, and by studying its impact on the air traffic.

The swirling movement of the air around the leader’s wake encountered by the following aircraft explains the benefits of the formation flight technique but can also lead to hazardous dynamic effects such as strong rolling moments. Nevertheless, those effects are disseminated information that can be interpreted by the follower in order to detect the position of the leader’s wake. In large eddy simulations, we aim to reproduce all those effects, from the aerodynamics of the aircraft to their six-degrees-of-freedom dynamics.

Then, we exploit control and data assimilation tools designed to predict the characteristics of the leader’s wake without requiring direct visual information. We show that the tracking of the wake can be performed using controllers built either from model-based Ensemble Kalman Filters or from model-free Reinforcement Learning techniques. We highlight observability issues related to the prediction of the wake characteristics and we use an appropriate mathematical framework to quantify that observability in order to optimize the wake tracking controllers. Finally, thanks to the development of methodology that combines both space-developing and time-developing simulations, we study the impact of formation flight on the long-term dynamics of the wake resulting from the two-aircraft formation. We highlight the strong asymmetry of the wake and the impact of the uncertainty of the relative position between the leader and the follower on its dynamics. We show the difference of this wake with the one produced by an isolated aircraft.

Jury members :

• Prof. Philippe Chatelain (UCLouvain, Belgium), supervisor
• Prof. Aude Simar (UCLouvain, Belgium), chairperson
• Prof. Grégoire Winckelmans (UCLouvain, Belgium)
• Prof. Julien Hendrickx (UCLouvain, Belgium)
• Prof. Mattia Gazzola (University of Illinois Urbana Champain, USA)
• Mr. Jordan Adams (Airbus, France)

Visio conference link

The autothermal chemical looping reforming (aCLR) is an alternative technology to steam methane reforming (SMR) and partial oxidation of methane (POM) aiming at solving CO₂ capture and improving their energy efficiency. The successful demonstrations of aCLR use mostly the toxic Ni-based or Ni-containing oxygen carriers that is problematic. Other oxygen carriers, e.g., Fe-based and Cu-based OCs, suffer from either low fuel conversion and/or agglomeration.

This thesis proposed the catalyst-enhanced aCLR, an environmentally compatible realization of aCLR, which uses Fe-based OC for oxygen transport and Rh-based catalyst for methane conversion. The intrinsic reaction kinetics of the Rh-based catalyst, the oxidation kinetics of the Fe-based OC are studied in a fixed bed reactor and the kinetics parameters are carefully estimated. This novel process is studied via multi-scale modeling that accounts for the detailed mechanisms, mass transfer between the emulsion gas and the catalyst particles, the mass transfer between the bubble phase and the emulsion phase, and the residence time distribution of OC particles on the reduction. This study found the novel catalyst-enhanced aCLR feasible, revealed the relative importance of kinetics and operating parameters, and provides a tool to analyze, design and optimize the aCLR/catalyst-enhance aCLR process efficiently.

Jury members :

• Prof. Juray Dewilde (UCLouvain, Belgium), supervisor
• Prof.  Renaud Ronsse (UCLouvain, Belgium), chairperson
• Prof.  Joris Proost (UCLouvain, Belgium)
• Prof. Mark Saeys (Ghent University, Belgium)
• Prof. Lunbo Duan (Southeast University, China)
• Dr. Arthur Pozarlik (University of Twente, Netherlands)

Visio conference link: https://teams.microsoft.com/l/meetup-join/19%3ameeting_NDY0ZWViNDEtMGJkMy00MzFlLTgwZDYtY2NkZGMyMWMxMGZi%40thread.v2/0?context=%7b%22Tid%22%3a%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2c%22Oid%22%3a%22566a57ca-a5e3-40be-88f2-55b3746064ca%22%7d

The exponential growth of technology opened the door for a new generation of locomotion assistive devices (e.g. prostheses and exoskeletons) to emerge. However, such systems still face several challenges regarding their interactions with human users. For instance, they usually lack the capability to timely detect the actions and intentions of the human wearer. Therefore, transitions between two locomotion modes – such as overground walking and stair climbing – are still handled in a reactive way. This thesis introduces a computer vision-based terrain detection algorithm for predicting locomotion modes. It relies on a depth camera attached to the user’s chest and an algorithm processing the acquired point cloud data to predict the terrain type and estimate its geometrical features for multiple steps in front of the user. Additionally, the system is equipped with an estimator of the walking stride length, speed, and turning angle, based on a single inertial sensor that is integrated in the depth camera. The algorithm is validated with 8 participants in several indoor and outdoor paths with a variety of terrain types. Moreover, validation is also achieved by conducting experiments with clear and partially occluded path conditions. Consequently, the thesis provides a validated software package consisting of terrain detection for multiple steps; estimation of geometrical features, speed, and turning angle; with and without partial occlusion. It can provide a valuable tool for a variety of disabled people including amputees with an active prosthesis, visually impaired, or blind people who face locomotion challenges in daily life.

Jury members :

• Prof. Renaud Ronsse (UCLouvain, Belgium), supervisor
• Prof. Hervé Jeanmart (UCLouvain, Belgium), chairperson
• Prof. Bruno Dehez (UCLouvain, Belgium)
• Prof. Christophe De Vleeschouwer (UCLouvain, Belgium) secrétaire
• Prof. Renaud Detry (UCLouvain, Belgium)
• Prof. Eren Erdal Aksoy (Halmstad University, Sweden)

In dynamic, mechatronic and robotic systems, a basic mechanical component for transmitting motion, force, and power between motor and load is a chain of gears. This type of transmission system is specifically effective for lightweight, small, but large output torque, for example, flapping wing micro aerial vehicles (FWMAV’s). Most of the times, the performance of these geared mechanisms are interrupted by backlash, friction, misalignment, and time-varying elasticity between mating teeth as well as shafts, all of them, exhibiting highly nonlinear phenomena. These phenomena have adverse effects on the motion and power transmission capability of a geared system. For example, for some moments, backlash may cause no rotation of driven shaft and its connected gear, then no leading-edge and wing motion of FWMAV (zero-output), while the DC motor is rotating the driver shaft and its mounting gear (input available). As another example, sliding friction of mating gear profiles will reduce the input energy conversion from electrical to useful mechanical energy, but converts a part of the input energy to some inaccessible heat and sound energy parts, limiting the battery life, in other words, there is some heat loss. As a third example, angular misalignment between center axes of mating gears may magnify both effects of backlash and friction, as well as interfere in the proper power transmission. There are some anti-backlash gear systems, which can reduce static and dynamic transmission errors due to backlash under some limitations, but they cannot reduce all the above-mentioned effects simultaneously. In addition, their servo-controllers need different routes for actuation and sensing, while piezoelectric transducers will do both jobs simultaneously. Moreover, there is the capability of micro/nano-positioning of piezo-actuators to receive the desired regulation and precision.

Dr. Hamid Reza Mirdamadi

Visiting Professor of Mechatronics and Robotics (ULB)

Birds have inspired human innovation and technology for centuries. The first documented human flying attempt dates back the late 800, from Abbas ibn Firnas who created what is considered the first aviation experiment. Later in the years, around the 15th century, Leonardo da Vinci dedicated long time of his research to formally understand bird's flight, leading him to the famous ornithopter invention. Biological fliers are still nowadays a source of scientic inspiration for unsolved research questions, both invoking a deeper understanding of sophisticated flight mechanisms, and sparking new engineering ideas.

This Thesis aims at contributing in the field of flight dynamics of migratory birds, trying to understand the role of biological and kinematic parameters on flapping flight stability. From a physical point of view, the flapping represents a forcing term in the equations of motion of bird flight. Generally speaking, due to this action, these equations do not display fixed points of equilibrium. The problem of studying stability of bird flight is therefore re-formulated via a limit cycle analysis of such equations of motion.

We leverage such a formalism to provide evidence that the morphological and kinematic parameters responsible for the generation of the pitching moment, are the most impacting the longitudinal stability. Our numerical results suggest that passive stability cannot be achieved in absence of the tail surface. However we show a trade-off between passively stable flights, and power expenditure, suggesting explanations for the elds observation that birds flap with furled tail during long flights.

We conclude by validating a multi-body approach for modeling the bird dynamics, that can be of direct help in understanding the role of bio-inspired compliant elements on flight stability. A preliminary investigation modeling the shoulder joint compliance of the wing is proposed.

Jury members :

• Prof. Renaud Ronsse (UCLouvain, Belgium), supervisor
• Prof. Philippe Chatelain (UCLouvain, Belgium), supervisor
• Prof. Sandra Soares-Frazao (UCLouvain, Belgium), chairperson
• Prof. Pierre-Antoine Absil (UCLouvain, Belgium)
• Prof. Emily Shepard (Swansea University)
• Prof. Mark Lowenberg (University of Bristol)
• Prof. Julien Hendrickx (UCLouvain, Belgium)

In this talk, we will focus on both the mathematical issues related to the use of zero-measure elements and the X-MESH resolution scheme. Several applications will be targeted: the Stefan model of phase change, two-phase flows and contact between deformable solids.

  Prof Jean-Francois Remacle

The minimization of nitrogen oxides (NO_x) emissions is among the major concerns of combustion-related processes, together with the adverse effects related to the emission of greenhouse gases. NO_x emission control can become very challenging for those combustion processes which require high temperatures, and/or involve the exploitation of non-conventional fuel mixtures. This PhD thesis work aims to shed light on NO_x formation during combustion of Coke Oven Gas (COG) and particularly to understand the role that aromatic chemical compounds could play during NO_x formation. COG is an attractive energy source derived from the coal carbonization, due to its high H₂ content and calorific value. It has been widely investigated as a fuel directly burnt in-situ to sustain the energy requirement of the integrated steel production processes, or as an important source of valuable compounds (i.e., H₂, CH₄, syngas, methanol, etc). The residual presence of aromatic compounds in COG, downstream the raw COG purification line, can potentially affect both its combustion efficiency and pollutant emissions. Therefore, a fundamental understanding of the interactions between NO_x formation and aromatic species oxidation is required to both valorize the use of COG as energy carrier, and to highlight promising strategies for the minimization of NO_x emissions during the combustion of COG in coke making plants. Benzene (C₆H₆) has been considered as the representative aromatic compound. The effect of its addition on NO formation chemistry, during combustion of COG surrogate fuel blends has been investigated, under different stoichiometric conditions. A hierarchical approach was used in this thesis work to achieve this objective. Indeed, NO_x formation during combustion of a COG surrogate mixture (H₂/CH₄/CO) has been investigated at i) lab-scale, in low-pressure flat premixed laminar flames through a joint experimental and kinetic modeling study, and at ii) semi-industrial scale, in a 20-kW semi-industrial furnace. The hierarchical approach adopted in this work allowed to highlight the main effects of benzene (C₆H₆) on NO formation during combustion of COG surrogate mixtures. Particularly, benzene was found to lead to two main competing effects in the COG flames: (a) increase of prompt NO, due to the increased production of the CH radical coming from intermediate species of the aromatic ring oxidation (direct chemical effect); (b) decrease of thermal NO when the local formation of soot particles enhances the emissivity of the flames, thus the efficiency of the heat transfer from the flame to its surroundings (indirect effect due to flame temperature reduction). The relative importance of the two effects determines the final NO_x emissions emitted from a combustion system fed with COG.

Jury members:

• Prof. Parente Alessandro (ULB, Belgium), supervisor
• Prof. Hervé Jeanmart (UCLouvain, Belgium), supervisor
• Prof. Axel Coussement (ULB, Belgium)
• Dr. Véronique Dias (UCLouvain, Belgium)
• Prof. Francesco Contino (UCLouvain, Belgium)
• Prof. Kevin Van Geem (Ghent University, Belgium)
• Prof. Maria Uxue Alzueta (University of Zaragoza, Spain)
• Dr. Phuc Danh Nguyen (ArcelorMittal Maizières Research, France)

Visio conference link :
https://teams.microsoft.com/l/meetup-join/19%3ameeting_NGNjMThhMDYtNWQ5OS00OTA0LTlhMDgtYTQ1MzU0NDMyNzBh%40thread.v2/0?context=%7b%22Tid%22%3a%2230a5145e-75bd-4212-bb02-8ff9c0ea4ae9%22%2c%22Oid%22%3a%221cd6a519-3eec-4340-873e-6d4718c58f53%22%7d

Laser Powder Bed Fusion (LPBF) is an additive manufacturing technique widely used in aerospace and automotive industries which allows the production of complex geometries. Aluminium is a material of choice for these industries thanks to its excellent strength-to-weight ratio but Al alloys currently used for LPBF present a low damage resistance. In order to increase parts lifetime, one promising solution is to use healable Al alloys. The objective of this PhD thesis consists in the development, characterisation and optimisation of new healable Al alloys manufactured by LPBF. Two healing strategies were investigated:

First, the programme damage and repair strategy is based on diffusion of healing agent (HA) towards the damage sites. 6xxx series Al alloys were selected as the most promising and a new efficient methodology was developed to optimise their manufacturing. Three alloy compositions were investigated but healing of voids up to 500 nm was demonstrated by 3D X-ray nano-imaging and heating in-situ TEM only in presence of Mg. The tensile properties were significantly changed during healing heat treatment (HHT) which is not desirable.  

Second, the eutectic strategy is based on the melting of the low melting point HA phase and can heal larger defects. The 5xxx series Al alloys were selected as promising compositions due to their large solidification range. The new statistical methodology allowed to optimise their LPBF manufacturing. 3D X-ray nano-imaging showed healing of voids up to 1 µm and even a crack of 12 µm. Moreover, the HHT induced a slight increase of the mechanical properties. The healing efficiency was significantly improved by the addition of pressure during HHT which even increases the fatigue resistance up to a factor 100.

Jury members :

• Prof. Aude Simar (UCLouvain, Belgium), supervisor
• Prof. Hervé Jeanmart (UCLouvain, Belgium), chairperson
• Prof. Ernst Kozeschnik (TUWien, Austria)
• Prof. Philip Withers (University of Manchester, UK)
• Prof. Alexis Deschamps (Université Grenoble Alpes, France)
• Prof. Anne Mertens (ULiège, Belgium)
• Prof. Hosni Idrissi (UCLouvain, Belgium)

Visio conference link : https://teams.microsoft.com/l/meetup-join/19%3ameeting_YjRlMzZmYmQtMzUwNS00OTQ2LTlmNGEtYTI5M2RhYWQ3NDVh%40thread.v2/0?context=%7b%22Tid%22%3a%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2c%22Oid%22%3a%22025f9711-d2b0-45fe-b3d9-73089a40e981%22%7d

For more than 3000 years, windmills have been used to harvest energy from the wind. Over the past 30 years, electrical generators and advanced aerodynamics have turned them into the wind turbines we know. From here on, how can the coming 30 years see them transition from outsider to key player of the energy system to help reach carbon neutrality? Increasing rotor diameters is a possible answer, clustering turbines into wind farms is another. Yet with both options come new challenges, as the sensitivity of components to fatigue increases with the size of rotors and the wake phenomenon is responsible for power losses in wind farms. This thesis falls in the context of using control strategies to tackle these challenges. More specifically, this work relies on high fidelity simulations to investigate control approaches numerically.

When it comes to reducing fatigue loads, individually controlling the pitch of each blade has proven to be efficient. This thesis introduces a novel controller architecture that relies on a neural network trained with reinforcement learning. This work demonstrates that a neural network can learn how to alleviate loads in simple wind conditions and that it is also capable of transferring that knowledge to realistic ones, such as turbulence and wakes.

On the question of wake mitigation, dynamically controlling wind turbines is gaining interest. While some strategies enhance the lateral displacement of the wake, others periodically modify its intensity. This work provides elements of answers regarding the mechanisms relating dynamic actuation of the blades to power gains in the wake. To do so, the effects of dynamic flow control on the wake destabilization and recovery processes are investigated. Attention is also paid to quantifying the impacts of such strategies on both power production and loads at the scale of a pair of turbines.

Jury members :

• Prof. Philippe Chatelain (UCLouvain, Belgium), supervisor
• Prof. Laurent Bricteux (UMONS, Belgium), supervisor
• Prof.  Sandra Soares-Frazao (UCLouvain, Belgium), chairperson
• Dr. Matthieu Duponcheel (UCLouvain, Belgium)
• Dr. Stéphanie Zeoli (UMONS, Belgium)
• Prof. Jan-Willem van Wingerden (TU Delft, Netherlands)
• Prof. Matilde Santos Peñas (Universidad Complutense de Madrid, Spain)

Visio conference link : https://teams.microsoft.com/l/meetup-join/19%3ameeting_ZTk4MjA0NjItZmQ3OS00Mzg4LThiNWQtNzIxMDdhM2ExODU1%40thread.v2/0?context=%7b%22Tid%22%3a%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2c%22Oid%22%3a%228ff4bb1e-789e-4a74-a035-cfd5d589272f%22%7d 

La gazéification est un procédé de conversion thermochimique de la biomasse utilisée dans des applications de production de chaleur et d’électricité. Ce procédé est prometteur dans un environnement ouest africain où les besoins énergétiques sont importants et où le potentiel en biomasse est considérable. La présente étude s’inscrit dans un contexte de valorisation par gazéification des résidus agricoles notamment la balle de riz. Elle a permis de concevoir et de fabriquer un réacteur de gazéification adapté aux petites unités industrielles dans le secteur de la transformation agricole.

Cette étude se décline en plusieurs étapes à savoir la mise en place d’une méthodologie de conception du prototype, la modélisation à l’équilibre de la composition du gaz produit, la simulation des pertes thermiques du procédé et la mise en œuvre d’une étude expérimentale sur le prototype. Plusieurs paramètres ont été étudiés expérimentalement à savoir le ratio d’équivalence, les niveaux d’injection d’air de même que le mode d’approvisionnement en combustible. Le gaz produit à l’issu du procédé de gazéification a été analysé afin de déterminer les conditions opératoires dans lesquelles le meilleur rendement a été obtenu.

Les meilleurs essais menés ont été réalisés à un ratio d’équivalence de 0,32 pour une puissance thermique de 50 kWth[PCI] et un rendement de 46 %. La composition du gaz obtenu est de 14,62 % de CO, 12,89 % de CO₂, 2,89 % de CH₄ et 6,84 % de H₂. Ces résultats avec un rendement relativement faible s’expliquent par les basses températures du procédé et une zone de réduction froide. En effet les pertes thermiques estimées à 8 % de l’ensemble du bilan d’énergie des entités sortantes du réacteur sont probablement plus élevées. Certaines difficultés opérationnelles telles que l’homogénéisation du lit au cours de gazéification conduit à la formation de by-pass où les gaz de pyrolyse sont entrainés vers la sortie. Cela explique également les proportions du gaz obtenu avec de faibles teneurs en CO et H₂. La campagne expérimentale menée sur le gazéifieur a permis d’émettre des perspectives pour améliorer les rendements pour de futurs travaux.

Membres du jury

• Prof. Hervé Jeanmart (UCLouvain, Belgium), supervisor
• Prof Grand Lat N'Diaye (Institut International d’Ingénierie de l’Eau et de l’Environnement 2ie, Burkina Faso), chairperson
• Prof. Aude Simar (UCLouvain, Belgium)
• Prof. Yézouma Coulibaly (Institut International d’Ingénierie de l’Eau et de l’Environnement 2ie, Burkina Faso)
• Dr. Sayon Sidibe (Institut International d’Ingénierie de l’Eau et de l’Environnement - 2ie, Burkina Faso)
• Dr. Benoît Herman (UCLouvain, Belgium)
• Dr. Oumar Sanago (IRSAT)
• Dr. Laurent Van De Steen (CIRAD)

Lien ZOOM : https://2ie-edu.zoom.us/j/96204495872?pwd=NjNKcW1lWnpHVUN0WjNYTTlOdGpuUT09

Mechanics is made of material but also immaterial movements. This is the case of the propagation of a crack or a solidification front. These movements are carried out without mass. Mechanics is therefore important even for physical phenomena for which there is no movement of matter.

The challenges posed by the modeling of immaterial surfaces are numerous from a numerical point of view. To be successful, it is important to consider theoretical and numerical modelling together.

In this talk, I will detail our contributions in Centrale Nantes on the theoretical and numerical modeling of some immaterial surfaces. Different topics will be reviewed such as cracking of quasi-fragile materials, contact and friction between solids, visco-plastic flows (threshold effect) or plastic instabilities (Lüders band and Portevin Le Chatelier effect). These subjects do not all have the same level of maturity in the achievements. They denote in appearance a great variety. We will explain the links that unite these subjects.

Speaker : Nicolas Moës, Ecole Centrale de Nantes

Hydrothermal alteration is near-ubiquitous at volcanoes worldwide and is thought to promote volcano instability and flank collapse. However, hydrothermal alteration can manifest as the dissolution/partial replacement of primary minerals within the rock, leading to an increase in porosity, or the precipitation of minerals within void space within the rock, leading to a decrease in porosity. In this seminar, we will explore what these end-member types of alteration do to the physical and mechanical properties of volcanic rock, and the stability of a volcanic structure. Using a combination of laboratory measurements and modelling, we reach the conclusion that porosity-decreasing alteration and porosity-increasing alteration can both promote volcano instability and collapse, but by different mechanisms. You'll have to attend the seminar to find out how and why! The take-home message is that hydrothermal alteration is never good news for a volcano and should therefore be monitored at volcanoes worldwide and incorporated into volcanic hazard assessments.

Speaker : Prof Michael J. Heap, Strasbourg University

assessment. The recent developments in Machine Learning techniques, able to capture the complex characteristics of wind generation, can be exploited to produce such models. Therefore, this work is aimed at developing data-driven models to improve the way offshore wind parks are considered within the current adequacy tools. These models are then included in an adequacy study built on sequential Monte-Carlo simulations and the impact of the improved offshore modelling on adequacy results is evaluated.

Speaker : Thuy-hai NGUYEN, UMONS

Friction Stir Welding (FSW) is a solid state (without fusion) welding technique involving no filler material. Patented for the first time in 1991 by The Welding Institute (Cambridge, UK), it consists in the mixing of the material of two parts to be assembled by a tool mounted on a CNC machine and applying friction and plastic deformation. Friction Stir Welding allows homogeneous or bi-material joints with a limited decrease in mechanical properties (compared to fusion welding processes) as well as an excellent repeatability as it is highly automated.

Initially applied to aluminum alloys, this process has been extended to other alloys with low melting temperatures, such as copper or magnesium. Numerous industrial examples using FSW on these alloys exist. Nevertheless, questions still remain regarding some mechanical properties of aluminium assemblies, particularly in the case of fatigue of so called “dissimilar” joints (welds containing multiple aluminum alloys). The thesis industrial partner, Thales Group, desired to better understand the specificities of this process and thus established a collaboration with UCLouvain and Ecole Polytechnique de Paris.

The thesis is centered on the dissimilar welding of AA6061 to AA7075 aluminum alloys. Particular attention is devoted to the impact of process parameters on previously described properties. A methodology is proposed to establish an optimized process window for AA6061/AA7075 with an emphasis on welds quality and thermal control. Selected similar and dissimilar joints are then characterized by various means: optical microscopy, Vicker hardness measurements and tensile testing using Digital Image Correlation (DIC). Links between these properties and process parameters used in the manufacturing of the joints are established. An innovative tensile test carried out inside a scanning electron microscope is presented in order to analyze local plastic deformation distribution inside the stir zone of a dissimilar joint. Finally, fatigue testing is carried out on selected welding conditions and relationships are established between thermal input during welding as well as stir zone morphology and fatigue life properties. Exploratory aluminum to titanium friction stir welds are presented and characterized in the appendix.

Jury members :

• Prof. A. Simar (UCLouvain, Belgium), supervisor
• Prof. E. Charkaluk (Ecole Polytechnique, France)
• Prof. H. Jeanmart (UCLouvain, Belgium), chairperson
• Dr. F. Hannard (UCLouvain, Belgium)
• Prof. J.-Y. Buffiere (INSA Lyon, France)
• Dr. M.-N. Avettand-Fenoel (Polytech Lille, France)
• Dr. T. Sapanathan (Curtin University, Australie)
• Dr. D. Weisz-Patrault (Ecole Polytechnique, France)

Visio conference link : https://teams.microsoft.com/l/meetup-join/19%3ameeting_ZjU4YzgzYjgtNGU5Ny00YTg5LThiNjItNzNmNTdmNjI3M2Zi%40thread.v2/0?context=%7b%22Tid%22%3a%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2c%22Oid%22%3a%22436fc3ab-3e42-4529-bca0-7978ab22718d%22%7d

Embedding particulate reinforcements in aluminum matrices to form aluminum matrix composites (AMCs) is an attractive, alternative and innovative process to enhance the mechanical properties of aluminum alloys. Shape memory alloys (SMA), e.g. NiTi (nitinol), are good candidates of reinforcement agents and have the unique property of being able to recover their shape before deformation throughout heating, the so called shape memory effect (SME).

Friction stir processing (FSP) was shown to be an appropriate manufacturing process for particulate AMCs due to mitigation of critical intermetallic formation between particles and matrix. Moreover, multiple FSP passes can homogenize the particles in the aluminum matrix. The present work aims at developing an innovative and functional Al 7075/NiTi composite incorporating internal stresses in the vicinity of reinforcements and understanding their effect on fatigue crack growth (FCG).

The internal stresses are introduced via SME of the embedded NiTi particles in the Al matrix. The patchwork of residual stresses induces dissipation of energy on the crack tip, in combination with crack trapping and deflection mechanism, enhancing fatigue crack growth resistance. The damage mechanism at the crack tip with the presence of internal stresses is investigated on FCG and correlated with the plastic zone size.

Jury members :

• Prof. Aude Simar (UCLouvain, Belgium), supervisor
• Prof. Thomas Pardoen (UCLouvain, Belgium)
• Prof. Renaud Ronsse (UCLouvain, Belgium), chairperson
• Prof. Lv ZHAO (Huazhong University of Sciences and Technology, China)
• Prof. Eric Charkaluk (Ecole Polytechnique, France)
• Prof. Leo Kestens (Ghent University, Belgium)

Visio conference link : https://teams.microsoft.com/l/meetup-join/19%3ameeting_YzkxOGRkOGUtYWIxMy00NWFlLTlmMTMtNjg5YWQ1ZTY2OTNk%40thread.v2/0?context=%7b%22Tid%22%3a%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2c%22Oid%22%3a%22ba2d3121-8905-462e-a553-c66f3f5c54ba%22%7d

In the current climate crisis, CO2 capture and utilization appears to be essential in achieving the climate targets and promoting the transition towards a society entirely relying on renewable energies. Among the alternatives, CO2 can be utilized as sodium bicarbonate salts, NaHCO3. This product is obtained by absorbing CO2 into Na2CO3 aqueous solutions, which are kinetically limited solvents. Nevertheless, adding promoters such as the biocatalyst carbonic anhydrase can enhance their absorption rate. The enzyme is exceptionally active and can work in mild conditions. However, enzymes are homogenous catalysts with limited stability. This issue can be addressed through enzyme immobilization on a support, as this approach leads to easier separation and enzyme conformational stabilization. In the targeted application, the immobilized enzyme must be placed close to the gas-liquid interface to fully take advantage of its catalytic properties. Thus, gas-liquid membrane contactors with carbonic anhydrase immobilized on the membrane surface are a promising technology for accelerating the absorption of CO2.

This work's novelty comes from employing ionic liquid-derived materials, mainly polymerized ionic liquids or poly(ionic liquid)s, a class of tunable CO2-philic polymers, to anchor the enzyme to the membrane surface. Different immobilization approaches were compared: entrapment, physical adsorption, and covalent bonding. The most promising results were obtained with the physical adsorption of carbonic anhydrase on hydrophilic poly(ionic liquid)s. The carrier was shaped as a thin film coating a porous hydrophobic support. The resulting biocatalytic composite membranes presented several interesting features, such as preservation of the native enzyme activity upon immobilization, excellent reusability, structural integrity, and a significant enhancement of the CO2 mass transfer. Indeed, the novel membranes increased the mass transfer of CO2 by a factor of 4.5 (in optimal conditions) compared to the commercial membrane support without any modification. Overall, the materials developed during this Ph.D. thesis displayed interesting performance for their application in CO2 capture and utilization.

Jury members :

• Prof. Patricia Luis Alconero (UCLouvain, Belgium), supervisor
• Prof.  Eric Deleersnijder (UCLouvain, Belgium), chairperson
• Prof. Damien Debecker (UCLouvain, Belgium)
• Prof. Patrice Soumillion (UCLouvain, Belgium)
• Prof. Grégoire Léonard (Université de Liège, Belgium)
• Dr Lidietta Giorno (National Research Council of Italy, Italy)
• Prof. Wojciech Kujawski (Nicolaus Copernicus University in Torun, Poland)

Teams link: https://teams.microsoft.com/l/meetup-join/19%3ameeting_ZTRhNjk0NzctOWRhNS00NjlkLWEyZmEtNWE4MTFjZDFkNDk3%40thread.v2/0?context=%7b%22Tid%22%3a%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2c%22Oid%22%3a%22ba2b0e66-a8f1-46da-8d8b-d02ab957aecc%22%7d

Wind Farm Flow Control (WFFC) refers to the coordinated control of the turbines inside wind farms with the goal of influencing the flow in such a way that it improves the global performances of the wind power plant. Gaining improved flow awareness is consequently paramount to enhancing the overall effectiveness and robustness of WFFC. Different avenues toward better flow awareness can be be pursued: (i) closed-loop control, (ii) improved flow-sensing techniques, (iii) more accurate, yet efficient, flow modeling. This thesis primarily focuses on the latter two approaches which are nonetheless prerequisites to efficient closed-loop control.

More specifically, it leverages Large Eddy Simulations (LES) of wind farms to support the development, tuning and testing of an operational dynamic flow modeling framework aimed at capturing the dynamic signature of the flow at a low computational cost while relying only on information gathered at the wind turbine location. The ensuing framework, named OnWaRDS, brings together flow sensing and Lagrangian flow modeling. The features of the inflow are first inferred from their blade load response: a Kalman filter coupled to a Blade Element Momentum theory solver is used to determine the rotor-normal flow velocity while an Artificial Neural Net trained on high-fidelity numerical data estimates of the rotor-transverse wind velocity component. The information recovered is in turn propagated in a physics-informed fashion across the domain by the Lagrangian flow model which contributes to incrementally reconstructing an estimated snapshot of the full wind farm flow field.

The ensuing framework is first presented and then deployed within a numerical wind farm where its performances are assessed. Comparison against the LES baseline reveals that the proposed model achieves good estimates of the flow state under various operating and atmospheric conditions. The model distinctly provides additional insight into the wake physics when compared to the traditional steady state approach: the characteristic signature of wake meandering along with the influence of large-scale fluctuations of the ambient flow are captured based solely on the information measured by the wind turbines. This analysis further confirms the computational affordability and high modularity of the proposed framework in line with the requirements of WFFC.

Jury members :

• Prof. Philippe Chatelain (UCLouvain, Belgium), supervisor
• Prof. Aude Simar (UCLouvain, Belgium), chairperson
• Prof. Grégoire Winckelmans (UCLouvain, Belgium)
• Prof. Julien Hendrickx (UCLouvain, Belgium)
• Dr. Thufe Göçmen (DTU, Denmark)
• Prof. Jeroen van Beeck (VKI, Belgium)

Join on your computer, mobile app or room device

Click here to join the meeting

Meeting ID: 311 005 081 788
Passcode: 4wf9CP

However, detailed kinetics mechanisms often require to solve hundreds of ordinary differential equations per computational cell, causing the need for massive computational resources. The Sample-Partitioning Adaptive Reduced Chemistry (SPARC) methodology, demonstrated to be effective in the speed-up of the chemical step of such costly simulations. This methodology couples adaptive chemistry and machine learning in order to build a library of locally reduced chemical mechanisms in the preprocessing step.

In this work, we present an enhanced version of SPARC which improves a number of critical aspects of the original methodology. In particular, we focus on the automatic selection of target species for reduction, and on the a-priori error estimation of the reduced mechanisms.

Industrial-scale simulations of fluidized bed reactors are currently performed using a Two-Fluid modeling approach, where both the gas and the particles are treated as inter-penetrating continua. Yet, the size of the mesh used is usually larger than the size of the mesoscale structures that appear in such gas-solids flows, namely clusters of particles.

Previous studies showed that neglecting the influence of these sub-grid scale (SGS) structures results in poor predictions of macroscopic bed properties. In this talk, two challenges regarding the SGS modeling of such flows will be discussed.

First, the SGS gas-particle drag term is shown to be the dominant contribution in the coarse-grid momentum conservation equation. The modeling of this term is based on the so-called drift velocity which arises from the correlation between the solid volume fraction and the gas velocity at the sub-grid scale. Until now, only functional models have been proposed, without much physical grounding. In this study, a novel modeling approach is proposed. We first derive a transport equation for the drift velocity itself. Fine-grid simulations of a tri-periodic fluidized bed reactor are then performed to obtain mesh-independent results and the data are spatially filtered to perform a priori analyses of the coarse-grid equations. A new explicit model is finally proposed where the drift velocity is expressed as a function of the resolved slip velocity and an algebraic function of a few moments of the solid volume fraction.

Second, we address the SGS modeling of granular temperature production. The correct estimation of the granular temperature on coarse grids is crucial for wall boundary conditions in the Two-Fluid framework, as well as for the simulation of polydisperse flows. In this regard, preliminary results based on an analogy with dissipation models used in single-phase Large Eddy Simulations will be discussed.

Speaker : Dr. Baptiste Hardy - postdoc at IMFT Toulouse

Although tribocharging has been known for centuries, the underlying mechanism is not fully understood. The complexity of the system and the number of variables affecting contact electrification makes it challenging to study experimentally. With the help of numerical tools and accurate mathematical models, it is now possible to study and help to predict the evolution of charge in such systems for industrial scale.

In this work, kinetic-theory-based transport models are developed for polydisperse granular and gas-solid flows accounting for contact electrification. The hydrodynamic and the additional charge transport models are assessed through hard-sphere simulation results. The mathematical models are used to study the effect of vessel size on charge build-up in gas-solid suspensions and to model lightning during volcanic eruptions.

Speaker : Lise Ceresiat - postdoc TFL

Immobilizing biocatalyst on the membrane surface in GLMC could potentially improve the CO2 capture performance of these green solvents. In this work, we compared the CO2 capture performance of cationic and anionic biopolymer coated on top of porous hydrophobic support. The type of porous hydrophobic support, polyelectrolyte coating concentration, membrane coating method, immobilization parameters and process conditions were evaluated. The works showed that the coating thickness, the type of polyelectrolytes coating and the type of porous hydrophobic support greatly influenced the CO2 capture performance. The immobilized biocatalyst onto anionic polyelectrolytes coating was able to improve the overall mass transfer coefficient (Koverall) compared to the cationic polyelectrolytes coating. In summary, anionic polyelectrolyte coating might be more suitable to be implemented as a biocatalyst immobilization platform in thin-film composite biocataltytic GLMC for CO2 capture applications.

Speaker: Yusak Hartanto

Yusak completed his PhD in Chemical Engineering at the University of Adelaide in 2016 with a thesis on desalination process. He then did a first postdoc at KU Leuven on forward osmosis and organic solvent nanofiltration. Since March 2020, he joined IMAP as a postdoc researcher to work on biocatalytic membranes for CO2 capture. CO2 capture is an important topic in today's world, don't miss your chance to hear from a young speaker who is undoubtedly at the forefront of this field.

Speaker : Humberto Varum is full professor and director of the PhD Program in Civil Engineering at the Faculty of Engineering of the University of Porto, Portugal. Since May 2015, he is member of the directorate body of the Construction Institute from the University of Porto, and President since May 2019. He has been Seconded National Expert to the ELSA laboratory, Joint Research Centre, European Commission, Italy, in the period July 2009 to August 2010. He was member of the Project Team 2 for the development of the 2nd generation of EN Eurocodes (SC8.T2 - material dependent sections of EN 1998-1).

Speakers:
•    Gustavo GARCIA, Associate Prof., Ritsumeikan University: garcia-g@em.ci.ritsumei.ac.jp (LinkedIn / Google Scholar):
Gustavo A. Garcia Ricardez received his MEng and PhD degrees from the Nara Institute of Science and Technology (NAIST), Japan, in 2013 and 2016, respectively. He is currently an Associate Professor at Ritsumeikan University, a Visiting Associate Professor at NAIST, and a Research Advisor at the Robotics Hub of Panasonic Corporation, where he leads numerous research projects and teams in international robotics competitions. His research interests include human-safe, efficient robot control, human-robot interaction, manipulation, and task planning. He is also the recipient of multiple research awards and competition prizes, an active member of RSJ and IEEE, and the CEO of G-ROBO KK.

•    Lotfi EL HAFI, Assistant Prof., Ritsumeikan University: lotfi.elhafi@em.ci.ritsumei.ac.jp (LinkedIn / Google Scholar):
Lotfi El Hafi received his MScEng from the Université catholique de Louvain, Belgium, and his PhD from the Nara Institute of Science and Technology, Japan, in 2013 and 2017, respectively. His thesis focused on STARE, a novel eye-tracking approach that leveraged deep learning to extract behavioral information from scenes reflected in the eyes. Today, he works as a Research Assistant Professor at the Ritsumeikan Global Innovation Research Organization, as a Specially Appointed Researcher for the Toyota HSR Community, and as a Research Advisor for Robotics Competitions for the Robotics Hub of Panasonic Corporation. His research interests include service robotics and artificial intelligence. He is also the recipient of multiple research awards and competition prizes, an active member of RSJ, JSME, and IEEE, and the President & Founder of Coarobo GK.

Speaker : Tuhfe Göçmen, chercheuse senior au Department of Wind and Energy Systems de Technical University of Denmark (DTU)

Speaker : Prof. Renaud Ronsse (iMMC/MEED - Louvain Bionic's)

Speaker: Morgan Rusinowicz graduated from the PHELMA engineering school (Grenoble-INP UGA, France) in 2019, specialising in materials science. He then completed his Ph.D. at the SIMaP laboratory of the University of Grenoble, supervised by Muriel Braccini and Fabien Volpi, finalized in 2022. The topic was the characterisation of the mechanical and electrical behaviour of ceramic/glass thin films (Cu2O, Si3N4, SiOCH) used in functional devices by an approach combining nanoindentation experiments coupled with electrical measurements and numerical simulations using the finite element method. Since early 2023, Mogan is now working as a post-doc at IMAP on electromechanical couplings in nanolaminate materials.

In 2.5 hours (13-15h30) and in teams, project yourself to 2050, discover the individual and collective levers of the transition to a low-carbon society, and identify the role you want to play in it!

Registration mandatory - before the end of the week - because (i) you will need to perform a quick exercise to prepare the workshop and (ii)  a simple free catering will be offered:

https://forms.office.com/Pages/ResponsePage.aspx?id=1JCwei76z068fEEntNWC7AJkkb02UQtHqHBnC1u_DjhUMko2N0YwSTNJODVUWUFQWlYxOVMyRFdaSi4u

Qu’est-ce que l’atelier 2tonnes ?

Cet atelier va vous permettre de découvrir les leviers individuels et collectifs de la transition vers un monde bas carbone, en créant en équipe votre propre scénario de transition bas-carbone jusque 2050.
Pour cela, nous allons simuler la transition en France à partir de vos empreintes carbone et de vos choix, et vous pourrez visualiser en temps réel leurs impacts sur l’évolution des émissions, au niveau individuel et au niveau collectif.
Une fois inscrit.e au sondage ci-joint, vous recevrez en temps et en heure une invitation pour calculer votre empreinte carbone.

Left-brain thinking tends to be analytical where superiority in maths and science can lead to successful careers in academic research. Right-brain thinking tends to be more intuitive and creative that, for example, reviews a broad range alternatives before deciding on a solution. Design tends towards right-brain thinking. A novel research program with evolutionary contributions to knowledge can be assisted by design thinking where a saturation of deep focused expertise can be disrupted, leading to a revolutionary contribution. Analogously, the inventor who focuses narrowly on the creation of a new idea can benefit from right-brain design thinking that can, for example, facilitate a broadened perspective. The development of experiments to test research hypotheses can also benefit from of design thinking. Various conceptual design tools can enable the researcher to maximise certainty that there is consistency between the various stages of a research program (aim, hypotheses, method and outcome – affirm or refute hypotheses), and in particular, the means by which the research hypothesis is tested (i.e. the experimental method). This presentation will offer two examples of the successful incorporation of design methods into research programs. Outcomes included: the trainee researcher had more clarity of the sought outcome of the program from the outset (i.e. affirm/refute original hypothesis); and, novel experimental equipment fulfilled their experimental objective on the first iteration (i.e. minimal iterative changes were required to the built equipment due to the exhaustive design effort, necessitated in part due to budget constraints). The two research programs were completed with the support of Professor Bruce Field and Dr Alan Smith, and are associated with the following PhD candidates who are now successfully traversing the words of academia, innovation and product development: Dr Paul Minty (

Speaker : Prof. Colin Burvill, University of Melbourne

Speaker: Selim Eskiizmirliler, Integrative Neuroscience and Cognition Center (INCC), CNRS UMR8002, Université Paris Cité, France

Afterwards, I would also like to present you a few more recent results that I will present in a poster in may. It will allow me to gather all your very interesting and precious insights about them! So please come in large number for this Friday’s seminar!

Speaker: Nicolas Nothomb started a PhD thesis in 2020 under the supervision of Pr. Aude Simar and in strong collaboration with Pr. Brecht Van Hooreweder of KULeuven. His research focuses on the improvement of fatigue life of high performance aluminium alloys produced by selective laser melting.

For the degree of Doctor of Engineering Sciences and Technology

Tensegrity – otherwise known as the art of floating bars in an ocean of cables – has fascinated a large scientific community for decades, though very few structures have been built. Why?

Together, during my public defense, we will investigate this question through the realizations of my numerical, analytical, and experimental developments.

In particular, I will detail a design, calculation, and optimization methodology for stiffness and mass, discuss the challenges of prestressing and erecting tensegrity structures, present the results of experimental testing on nearly real scale prototypes, and summarize the design guidelines for civil engineering applications.

I invite you to join me at my defense to learn more about this fascinating topic.

Jury members :

• Prof. Pierre Latteur (UCLouvain, Belgium), supervisor
• Prof. Eric Deleersnjider (UCLouvain, Belgium), chairperson
• Prof. Jean-François Remacle (UCLouvain, Belgium)
• Prof. Vincent Denoël (ULiège, Belgium)
• Prof. Landolf Rhode-Barbarigos (University of Miami, USA)
• Prof. Andrea Micheletti (University of Roma 2, Italy)
• Prof. Julien Averseng (Université de Montpellier, France)

Link of the videoconference (Teams) : https://teams.microsoft.com/l/meetup-join/19%3ameeting_MjZhNzY3YmMtYzljNy00MWUwLTliMGEtNzAwYTFhYmVhYWJm%40thread.v2/0?context=%7b%22Tid%22%3a%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2c%22Oid%22%3a%2261f4c456-3a33-4042-a54e-0fb7240811ae%22%7d

In the context of the structural integrity assessment of nuclear reactor pressure vessels (RPV), the mini-CT specimen is gaining worldwide attention as one of the ideal miniaturized geometries for measuring fracture toughness. This geometry is particularly appealing for several reasons. Firstly, up to eight mini-CT specimens can be machined out of one broken Charpy specimen, thus avoiding the need to consume additional surveillance materials. Secondly, the geometry permits specimen reorientation, which facilitates the investigation of anisotropic effects. Another considerable advantage that enables this geometry to replace large ones is that the mini-CT geometry have shown potential to produce fracture toughness results equivalent to large samples.

However, the miniaturization of test geometries induces a loss of constraint, which may lead to deviation of fracture toughness values when compared to those measured from larger geometries. In addition, due to the reduction in size, this geometry does not fully satisfy the ASTM requirements with respect to the varies ratios of the specimen dimensions. In particular, the requirements relative to the pre-crack front curvature and initial crack length are challenging, leading to a large number of mini-CT specimens not fulfilling the standard requirements and therefore being considered invalid. Therefore, in this thesis, three main issues in using mini-CT geometries: 1) effect of constraint loss, 2) effect of pre-crack front non-uniformity, and 3) effect of initial crack length are investigated to promote the standardization of the mini-CT geometry in both brittle and ductile regimes. The results demonstrate that, by implementing the adjusted specifications given in this thesis, the mini-CT geometry is capable of producing reliable and accurate fracture toughness measurements.

Jury members :

• Prof. Thomas Pardoen (UCLouvain, Belgium), supervisor
• Prof. Ludovic Noels (ULiège, Belgium), supervisor
• Prof. Eric Deleersnijder (UCLouvain, Belgium), chairperson
• Prof. Aude Simar (UCLouvain, Belgium)
• Dr. Benoit Tanguy (CEA, France)
• Dr. Philippe Spatig (EPFL, Switzerland)
• Dr. Inge Uytdenhouwen (SCK CEN, Belgium)
• Dr. Rachid Chaouadi SCK CEN, Belgium)

The link of the videoconference (Teams) and/or the audience you wish to book and the number of people expected

https://teams.microsoft.com/l/meetup-join/19%3ameeting_ZDA2MGQxZjQtYTEyMy00Yjg0LWFmYzAtMTIwOGEyMDAzYTA0%40thread.v2/0?context=%7b%22Tid%22%3a%222f885e27-9e8b-4e12-bf50-1768b073bc54%22%2c%22Oid%22%3a%221b58bc1b-58b2-4009-ab3b-f2377fb78ab2%22%7d

A new electrochemical pathway for cement production has gained prominence in the scientific literature in recent years [1]. This technology has the potential to electrify the cement and lime production while producing at the same time valuable gases (O2, CO2, H2). It is based on a new type of hybrid electrolyser capable of working with solid, liquid and gaseous phases. Thanks to the acidity generated by water oxidation at the anode, the solid limestone feed, precursor of cement, is being dissolved. This dissolution produces pure CO2 which is mixed with pure O2 generated by electrolysis and which is easily captured for later use. The calcium ions are then migrating towards the cathode under the effect of the electric field. The OH- hydroxyl ions, produced at the cathode by water reduction, meet the calcium ions to form the final solid product, hydrated lime (Ca(OH)2). This lime can be used as such or converted into cement by additional steps.

Speaker : Maxime Loudeche graduated at UCLouvain last year and is now working on the Faraday Project under the supervision of Prof. Joris Proost.

Étudier l’ébullition à basse pression au sein d’un bassin permet l’atteinte de conditions de nucléation spécifiques : le flashing d’eau métastable. Si ce phénomène peut apparaître dans d’autres configurations (geysers, réservoirs dépressurisés), le dispositif expérimental original Aquarius conçu pour ce besoin permet de révéler les spécificités d’une variation des conditions de saturation induite par la pression hydrostatique couplée avec un transport de chaleur et d’espèces gazeuses dissoutes par convection naturelle. Il s’agit ainsi de reproduire à petite échelle une situation à même de se produire lors d’un accident de perte de refroidissement au sein des piscines d’entreposage de combustible nucléaire des réacteurs de production électrique. Ces travaux de thèse déterminent les conditions d’existence d’eau métastable au sein du bassin, avec des surchauffes pouvant atteindre de 1 à 5°C, dans la zone située sous la surface libre. Une nucléation y est observée et le dispositif a permis d’étudier l’influence de plusieurs paramètres sur son occurrence : la puissance de chauffe, le niveau de pression, la hauteur d’eau, la quantité de gaz dissous. Une analyse théorique des mécanismes de nucléation est proposée et identifie la flottaison libre de nuclei gazeux comme un mécanisme probable, ce qu’il conviendrait de prouver par une instrumentation adéquate. En outre, une analyse quantitative de l’ensemble des mécanismes de transport de masse, de chaleur et d’espèces au sein du bassin permet de proposer un ensemble de coefficients d’échange et de corrélations. Une modélisation par une approche de type code à zone, incluant ces propositions de modèles permet enfin de reproduire avec une incertitude modérée l’ensemble du transitoire des tests considérés.

Jury members :

• Prof. Yann Bartosiewicz (UCLouvain, Belgium), supervisor
• Prof.  Hervé Jeanmart (UCLouvain, Belgium), chairperson
• Prof.  Matthieu Duponcheel (UCLouvain, Belgium)
• Dr. Pierre Ruyer (IRSN)
• Prof. Benoit Stutz (Université de Savoie, Mont Blanc, France)
• Prof. Masahiro Furuya (Waseda University, Japan)

Speaker : Jimmy Martin

Teams : https://teams.microsoft.com/l/meetup-join/19%3ameeting_NDc3ZTg0MzgtOGU1OC00NjRkLWFkYjUtOTYyYWEyMDZkZWI2%40thread.v2/0?context=%7b%22Tid%22%3a%2275524cf4-d5bf-43cc-b98f-a2a5047dfea2%22%2c%22Oid%22%3a%22857a6fb3-9bdc-4848-a063-95384c55b0bf%22%7d

Speaker: Marco Endrizzi, Department of Medical Physics and Biomedical Engineering, University College London

In this seminar, the first steps of this work will be presented, i.e. the investigation of the influence of processing conditions on the development of the crystalline phase of the semi-crystalline matrix. In addition, a study of the local mechanical properties and behavior of the same carbon fiber-reinforced thermoplastic will be discussed through nanoindentation tests and in-situ transverse compression in a scanning electron microscope (SEM) followed by nano-scale digital image correlation (DIC) of the unidirectional composite. Finally, the impact of crystallization conditions on the macroscopic mechanical behavior of the composite will be discussed.  

Speaker: Sophie Vanpée is a PhD student under the joint supervision of Thomas Pardoen and Bernard Nysten (BSMA), in partnership with Solvay company. She is studying the micromechanics of high-toughness composites.

Speaker : David Henneaux

Speaker : Prof. Olga Klinkova, from ISAE-Supméca (Paris),

Speaker: Charline van Innis is a FRIA-funded PhD student, supervised by Thomas Pardoen, studying new toughening solutions for composite/metal joints.

Academia and industry have thus far proposed two numerical solutions to tackle such flows.
A first one consists in vorticity-based Lagrangian methods, or vortex methods in short. Such techniques enjoy some computational benefits that are particularly interesting for the resolution of the wake regions. However, vortex methods are ill-suited to capture high Reynolds number boundary layers because of their intrinsic isotropic computational elements. A second group of methods gathers Eulerian body-fitted grid solvers, such as finite differences, finite volumes, finite elements, etc. They allow the use of anisotropic computational elements that conform to the body and are ideally suited to capture the boundary layers; their Eulerian handling of advection however causes them to fall behind in the capture of the wake because of the involved dispersion and diffusion errors.

This naturally leads to the proposition of combining the complementary advantages of Lagrangian vortex methods and body fitted-grid solvers in a coupled approach.

This thesis proposes a novel weak coupling to perform this in a computationally efficient manner. In particular, it improves upon pre-existing efforts that often led to noisy, and thence not exploitable, aerodynamic efforts and lacked robustness in the conservation of circulation.
This new coupling methodology has been developed and implemented for two types of body-fitted solvers: finite volumes and finite differences. Its performance is verified on the benchmark problem of the flow past a cylinder, both in an impulsive start and in a shedding regime.

Jury members :

  Prof. Grégoire Winckelmans (UCLouvain, Belgium), supervisor
  Prof. Philippe Chatelain (UCLouvain, Belgium), supervisor
  Prof. Renaud Ronsse (UCLouvain, Belgium), chairperson
  Prof. Laurent Bricteux (Umons, Belgium)
  Dr. Matthieu Duponcheel (UCLouvain, Belgium)
  Prof. Pierre Bénard (INSA Rouen Normandie, France)
  Prof. Carlos Simão Ferreira (TUDelft, Pays-Bas)

Link Teams : https://teams.microsoft.com/l/meetup-join/19%3ameeting_YjA5NzYwMjQtMzFiOC00Y2VlLTkyMzktMzNkZTBhMTY0NWM2%40thread.v2/0?context=%7b%22Tid%22%3a%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2c%22Oid%22%3a%22f71c1638-4a35-46da-9dda-9a3cb1c37a89%22%7d .

The binary Ti-12 wt% Mo grade produced by mixing the pure powders was chosen as the case study. The mechanical properties of the printed parts were first verified by tensile tests. Uniform elongation and work hardening similar to those in the wrought state (casting, rolling, recrystallisation) were achieved after a simple flash heat treatment, while the yield strength of the printed samples was increased by 20%. In situ X-ray tomography follow-up of certain tensile tests also revealed that the presence of defects (porosities, unmelted molybdenum particles) does not have a strong impact on the fracture mechanism of this alloy. In addition, a comparison with printed TA6V shows that although the void nucleation rate is greater in printed Ti12Mo due to the breakage of unmelted molybdenum particles, the acceleration of growth only occurs later. This delay in coalescence can be explained by the strain-hardening of the material ligaments present between the cavities, as revealed by the nano-indentation tests carried out along these ligaments.

Speaker: Marion Coffigniez defended her PhD on additive manufacturing of 3D architectured metallic biomaterials by robocasting in 2021 at MATEIS, INSA-Lyon. Now she is working on additive manufacturing of beta metastable titanium alloys presenting both TRIP and TWIP effects.

Durant 30 minutes vous participerez à une exploration fascinante des pratiques testées durant 5 ans avec des étudiants ingénieurs. Nous parlerons entre autre de motivation des étudiants, de l’utilisation de rappels et de correctifs, de la mise en place de feedbacks, … dans le but de vous donner envie de tester de nouvelles pratiques.

Nous vous invitons à partager vos expériences en répondant à une courte enquête pré-séminaire. Cela permettra de mieux comprendre vos pratiques actuelles et d'identifier les défis auxquels vous êtes confrontés. Ensemble, nous pourrons discuter de celles-ci et peut-être que vous repartirez avec des outils pratiques, et une vision renouvelée pour créer des séances d'exercices stimulantes et efficaces.
 
 

Speaker: Maïté Croonenborghs is doing a Ph.D. thesis under the supervision of Pascal Jacques and Thomas Pardoen in the field of implant materials. She also has a passion for education and pedagogy.

The design of emerging energy systems relies on limited market data and long-term forecasts, leading to significant uncertainty in critical model inputs such as efficiencies, resource availabilities, fuel prices and investment costs. We consistently underestimate these uncertainties due to our reliance on the ordinary and the predictable, neglecting exceptional scenarios. This leads to a substantial mismatch between simulations and reality, potentially resulting in a kill-by-randomness of the energy system.

The seminar will be divided into three parts. Part one presents a computationally-efficient method to propagate input uncertainties through expensive models, allowing for a quantification of the resulting uncertainty on the performance (e.g., total system cost). Part two focuses on optimizing the design variables (e.g., number of photovoltaic panels, battery size) for expected performance, robustness, and upside variability. Lastly, we introduce a metric for optimizing antifragility, enhancing positive outcomes when the real-world uncertainties surpass the initial estimations made during simulation.

Even though this workshop focuses on energy systems, the method is non-intrusive and can be easily applied to any other system in any other field.

The recent development of Elium, a range of thermoplastic monomer formulas compatible with liquid composite moulding processes, has initiated the transition from thermosetting to thermoplastic polymer matrices for the manufacturing of structural composite parts. However, Elium remains a whole new resin system and, as such, must continue to prove its worth to the composite industry. This thesis lies at the heart of the ongoing research effort directed towards manufacturing fibre-reinforced Elium composites, understanding the mechanisms occurring during processing and how these impact the structural behaviour of the parts under mechanical loading. From an industrial perspective, mitigating void formation in thick (> 1 cm) Elium laminates manufactured by vacuum infusion followed by in-situ polymerisation was the first motivation for this work. The second, more fundamental objective was to contribute to the understanding of Elium composite properties at the microscale.

Through the development of a thermokinetic model, the main mechanism leading to void formation in Elium composites, i.e. monomer boiling during polymerisation, could be accurately captured. For any set of preform thickness, resin formula and fibre volume fraction, the model allows predicting whether the monomer will boil or not depending on the selected heating parameters. A miniature in-situ infusion experiment followed by dynamic X-ray computed tomography was also designed for monitoring void formation events in thick Elium laminates during processing. The results confirmed the particular sensitivity of the polymerisation step to void formation.

The deformation and failure mechanisms occurring at the constituent level in Elium composites were explored via a newly-developed nanoscale digital image correlation (DIC) method. Strain localisation events were exclusively observed in a thin (a few 100 nm) crown of matrix surrounding the fibres. This region was found to be the interphase region of the composite, beyond which the mechanical response of the polymer remains broadly similar to that of an unreinforced Elium resin.

Jury members :

• Prof. Thomas Pardoen (UCLouvain, Belgium), supervisor
• Prof. Christian Bailly (UCLouvain, Belgium), supervisor
• Prof. Hervé Jeanmart (UCLouvain, Belgium), chairperson
• Prof. Bernard Nysten (UCLouvain, Belgium)
• Dr. Pierre Gérard (Arkema, France)
• Prof. Yentl Swolfs (KU Leuven)
• Prof. Véronique Michaud (EPFL, Suisse)
• Dr. Julie Diani (Ecole Polytechnique Paris, France)

Visio conférence link : https://teams.microsoft.com/l/meetup-join/19%3ameeting_NTQ3MzBjZDktM2E5OC00YTIyLWE4Y2UtNzBjZTcwMTlkZGM2%40thread.v2/0?context=%7b%22Tid%22%3a%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2c%22Oid%22%3a%223b538b2d-1afb-47fe-8739-f4a7614af4c1%22%7d 

Speaker : Kathryn Stok is an innovative bioengineer in microstructural imaging and biomechanics of cartilage and joint structures using a variety of experimental and computational approaches. Her research work merges solid engineering approaches with biological advancement.

Speaker: more info on Hosni's research topics here: https://www.youtube.com/watch?v=TzUzfJRv7Yk

Speaker: Sara Chergaoui is a Ph.D. candidate with prof. Patricia Luis, investigating a new strategy to antisolvent crystallization using porous membranes.

Nonlinear dynamic analyses of buildings and infrastructure use viscous damping models to represent energy dissipation sources independent of the materials' constitutive rules. These mechanisms correspond to connections, the interaction between structural and non-structural elements, and the interface between concrete and steel, among others. All these complex sources of energy dissipation have been considered indirectly through viscous damping models since they are expected to have no significant influence on the structure's response. However, it is well known that these models can significantly affect the results when the system enters the inelastic range. This thesis addresses this problem by suggesting modifications for existing models and new approaches. Initially, it is proposed to eliminate the geometric stiffness matrix from the definition of a tangent stiffness proportional viscous damping model. Then, a new condensed damping model proportional to the tangent stiffness matrix is presented to reduce the high energy dissipation caused by the existing condensed models. Finally, new non-linear damping models are formulated that allow limiting the damping forces to reasonable levels, ensuring that the assumptions initially used to implement viscous damping models are fulfilled.

Jury members :

• Prof. Issam Doghri (UCLouvain, Belgium), supervisor
• Prof. Jean-François Remacle (UCLouvain, Belgium), supervisor
• Prof.  Hervé Jeanmart (UCLouvain, Belgium), chairperson
• Prof.  Hervé Degée (Hasselt University, Belgium)
• Prof. Vincent Legat (UCLouvain, Belgium)
• Prof. Pierre Jehel (Université Paris-Saclay, France)

Visio conference link : https://teams.microsoft.com/l/meetup-join/19%3ameeting_Mzk4N2VhMzEtMDliMy00YjMyLTg5YjUtMTgxNDU1ODE0ZDRi%40thread.v2/0?context=%7B%22Tid%22%3A%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2C%22Oid%22%3A%220dcf96df-974f-429d-a6cb-aa70025d5c7e%22%2C%22IsBroadcastMeeting%22%3Atrue%2C%22role%22%3A%22a%22%7D&btype=a&role=a

Speaker: Armand Béché (https://www.linkedin.com/in/armand-b%C3%A9ch%C3%A9-08139b28/)

Immersed granular materials are implied in many different fields. From blood flow to volcanic eruptions, and through the agro and chemical industries, they cover a wide range of scales.
The ability to describe and predict the way they flow and behave under external constraints is therefore crucial.

However, because of the divided nature of the granular media, these materials exhibit complex behaviours, as they can flow like a liquid and resist shear like a solid. The various interactions between the grains and the fluid phase further adds to the overall complexity. In many aspects, friction plays a key role, and so does the grain shape.
Numerical models emerged as useful tools to investigate the properties of such materials, but remain bound to the computational costs they result in. In order to limit those, a multi-scale model that takes friction and grain shape into acccount is presented. The granular phase is solved on the grain scale with a Lagrangian method and arbitrary grain shapes are modeled as clusters of disks or spheres. The fluid phase is solved on a larger scale by considering volume-averaged Navier-Stokes equations.

The model was used to study applications where friction or grain shape play a key role, such as the  force exerted on a rigid body in an immersed granular flow or the column collapse of elongated grains. In the first application, the results shed light on the influence of friction, and on the different flowing regimes and their characteristics. In the second case, the effect of orientational features specific to elongated grains were described, and an energy-based approach was suggested to describe the mobility of collapsing columns.

Jury members :

• Prof. Vincent Legat (UCLouvain, Belgium), supervisor
• Dr. Jonathan Lambrechts (UCLouvain, Belgium), supervisor
• Prof. Aude Simar (UCLouvain, Belgium), chairperson
• Prof. Evelyne Van Ruymbeke (UCLouvain, Belgium)
• Dr. Frédéric Dubois (Université de Montpellier, France)
• Dr. Emilien Azéma (Université de Montpellier, France)
• Prof. Geoffroy Lumay (ULiège, Belgium)

Visio conference link : : https://teams.microsoft.com/l/meetup-join/19%3ameeting_NTIzYTcwMjUtMjJhMS00OTNiLWIzMDYtM2NhODExZWFjNjNi%40thread.v2/0?context=%7b%22Tid%22%3a%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2c%22Oid%22%3a%225a7e02ff-76a3-4760-938e-fab03dc078da%22%7d

Despite the continuous improvement of prevention and treatments, cardiovascular diseases are the most common cause of death in the world. They correspond to (micro)structural changes affecting the proper functioning of the cardiovascular system. To non-destructively assess the complex and heterogeneous 3D structural organization of the heart and its constituents (heart chambers, coronary blood vessels, muscle fibers and heart valves), advanced imaging techniques are required.

This thesis was dedicated to the optimization and application of microfocus computed tomography (microCT)-based imaging techniques, such as contrast-enhanced computed tomography (CECT) and cryogenic CECT (cryo-CECT) to the entire heart (murine) and the heart valves (porcine and human). First, cryo-CECT, in which the biological samples are frozen and preserved frozen during the entire image acquisition, was optimized on bovine muscle samples to visualize individual muscle fibers. It was then applied to hypertrophic and control murine hearts to demonstrate the ability to perform 3D histopathology of biological samples. It allowed to compute the orientation and thickness of individual muscle fibers in the myocardium. Then, CECT and cryo-CECT were compared using two imaging qualities to perform 3D histology of healthy murine hearts. The microstructure of the coronary blood vessel network and the 3D thickness distribution of the left-sided heart valves were characterized in a non-destructive way.

In the second part of the PhD thesis, human calcified aortic valves (associated with aortic stenosis) were analyzed using high-resolution microCT (without contrast-enhancement) to quantitatively describe the calcifications present in the cusps, as well as the changes in the soft tissues surrounding the dense calcifications. This detailed microstructural characterization was obtained for two diagnosis groups and paves the way for a better understanding of the calcification mechanisms involved in aortic stenosis. Finally, CECT and cryo-CECT were applied to healthy porcine mitral valves to determine their microstructure in full 3D. While CECT surprisingly revealed the presence of adipocytes and a complex blood vessel network, cryo-CECT enabled the visualization of the organization of extracellular matrix fibers within the porcine mitral valve leaflet. Both techniques were finally applied to a chorda tendinea sample (connecting the mitral valve leaflet to the papillary muscle), and revealed the intricate transition from collagen towards muscle fibers.

Jury members :

• Prof. Greet Kerckhofs (UCLouvain, Belgium), supervisor
• Prof. Benoît Lengelé (UCLouvain, Belgium), supervisor
• Prof.  Hervé Jeanmart (UCLouvain, Belgium), chairperson
• Prof.  Christophe Beauloye (UCLouvain, Belgium)
• Prof. Nele Famaey (KU Leuven, Belgium)
• Prof. Christophe De Vleeschouwer (UCLouvain, Belgium)
• Dr. Romain Capoulade (Université de Nantes, France)

Visio conference link : https://teams.microsoft.com/l/meetup-join/19%3ameeting_ZjBjZDlmZjEtZmJhYy00YTljLWE5OGUtZDAwNzBmOWRjNTU4%40thread.v2/0?context=%7b%22Tid%22%3a%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2c%22Oid%22%3a%2210b0b9f0-5658-4559-a3a1-282e64075124%22%7d

High-performance micromotors are becoming ubiquitous through a wide variety of applications that require both high power density and high efficiency. Examples include reaction wheels for the precise positioning of satellites, active prostheses, and surgical power tools. Electric motors that use permanent magnets (PM) typically provide the highest power density and efficiency and are therefore best suited for these applications. These PM motors can be classified based on their stator topology, in either the slotted or slotless topology. Furthermore, various winding variants exist, especially within the slotless topology. One particular slotless winding variant is the use of flexible printed circuits for replacing the traditional round copper wire, offering significant gains in performance. Depending on the application, one choice of topology and winding might be better suited than the other. However, there exists no rigorous comparative study and as a result, the choice is usually made on a case-by-case basis, without proper knowledge of the optimal selection.

Consequently, the main objective of this thesis is to rigorously and systematically compare the slotted and slotless PM topologies and their winding variants based on power density and efficiency, for a wide range of applications and operating conditions. To fulfill this objective and rightfully compare the different motor variants, they need to be extensively described, accurately modeled, and properly optimized to reach the highest possible performance. Performance maps are generated and used to visually compare the different motor variants based on their operating conditions. Finally, these maps are exploited and validated on a particular cycle-based motor application, namely an active ankle prosthesis.

Jury members :

• Prof. Bruno Dehez (UCLouvain, Belgium), supervisor
• Prof. Hervé Jeanmart (UCLouvain, Belgium), chairperson
• Dr. François Baudart (Mirmex Motor, Belgium)
• Prof. Renaud Ronsse (UCLouvain, Belgium)
• Prof. Alexander Badri-Sprowitz (KU Leuven, Belgium)
• Prof. Elena Lomonova (TU Eindhoven, The Netherlands)

Visio conference link : https://teams.microsoft.com/l/meetup-join/19%3ameeting_ZDBjMzhiNzUtNTNmYi00YTk3LWJmMDUtMDc1OTM5YjkzNWY3%40thread.v2/0?context=%7b%22Tid%22%3a%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2c%22Oid%22%3a%22b9d473c9-2e60-4c18-8c60-eefba6636e37%22%7d

Particle dispersion and deposition in a fully developed turbulent channel flow are investigated using direct numerical simulation. The combined effect of gravity and the Saffman lift force on the particle deposition velocities in upward and downward channel flows are considered. The results are compared with recent experimental measurements and numerical benchmark solutions. The importance of inertial particles accumulation in the buffer layer on the augmentation of particles deposition is discussed. On the modeling side, the effect of filtering the velocity field on deposition velocity is reported. The success of using a stochastic approach to model the subgrid-scale fluctuations of velocity seen by particles for the prediction of particles concentration and deposition is discussed.

Speaker : Prof. B. Lessani (University of North Carolina - Charlotte)

Climate change is an urgent challenge nowadays. The constant accumulation of greenhouse gases and their drastic consequences have led to intensified research aiming to reduce the impact of human activities on the environment. As carbon dioxide (CO2) is the primary greenhouse gas emitted through human activities, in the last years, numerous projects focused on the reduction of CO2 emissions have been raised. The more sustainable approach to reducing CO2 emissions until now is Carbon Capture and Utilization, which gives value to carbon by transforming it into another reusable product.

In this thesis, CO2 is considered a source of carbon that is worth recovering as a salt that can be reused in the industry. The process is based on the use of membrane technologies to capture and convert CO2 into high-purity sodium bicarbonate (NaHCO3) as a final product. The process is divided into two steps: first, the CO2 is captured in a membrane base absorption process using a solvent promoted by the Carbonic Anhydrase enzyme. Then, the resulting solution is concentrated up to crystallization in a membrane contactor.

The process has shown promising results and it can be considered a competitive option to the conventional CO2 capture process.

This process is protected by the patent WO 2022/117800 A, published on 9th June 2022.

Jury members :

•     Prof. Patricia Luis Alconero (UCLouvain), supervisor
•     Prof. Hervé Jeanmart (UCLouvain), chairperson
•     Prof. Denis Dochain (UCLouvain), secretary
•     Prof. Iwona Cybulska (UCLouvain)
•     Prof. Diane Thomas (UMons)
•     Prof. Jose Luis Cortina (Universitat Politécnica de Catalunya, Spain)

Visio conference link : https://teams.microsoft.com/l/meetup-join/19%3ameeting_ZGY2Y2JmZWEtYWU1MC00OTgxLWE1MDAtNmI5MzNmZTcyYjVj%40thread.v2/0?context=%7b%22Tid%22%3a%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2c%22Oid%22%3a%22c24dd004-b1df-4bbd-a1e5-e99bd26acd2e%22%7d

When a liquid is in contact with a solid surface, physico-chemical phenomena occur at the interface, leading to the formation of the electrical double layer. Inside the liquid, the electrical double layer comprises the Stern layer corresponding to a thin region adjacent to the solid/liquid interface, and the diffuse layer, whose the concentration of free ions decreases away from the Stern layer. Accordingly, flow electrification takes place when a flowing liquid, in contact with a solid, transports electric-charge carriers (ions) from the diffuse layer towards the bulk of the flow domain. This motion, in turn, generates a streaming current that is deemed responsible of major electrostatic accidents in the petrochemical industrial sector. Although studied extensively during the last 50 years, this phenomenon is currently not well understood, notably because of the inherent complexity of flow turbulence. Indeed, conclusive studies about the role of turbulence and the underpinning mechanisms of turbulent flow electrification are still lacking. Therefore, this thesis studies in detail the phenomenon of electrification of flowing dielectrics liquids, notably in turbulent channel flows.

Jury members :

•    Prof. Miltiadis Papalexandris (UCLouvain, Belgium), supervisor
•    Dr. Holger Grosshans (PTB, Germany)
•    Prof. Sandra Soares-Frazao (UCLouvain, Belgium), chairperson
•    Prof. Philippe Chatelain (UCLouvain, Belgium)
•    Dr. Christos Varsakelis (Janssens Pharmaceutical Companies of Johnson & Johnson, Belgium)
•    Prof. Ionel Sorin Ciuperca (Université Claude Bernard Lyon – 1, France)

Visio conférence link : Meeting ID 351 975 230 051   Passcode : GbJQD5

With the advancement in membrane characterization techniques, our understanding and knowledge of pervaporative membranes have significantly improved. Using the "Preferential Sorption-Diffusion and Capillary Flow" concept as a guide, high-efficiency pervaporation membranes for MeOH and DMC separation were designed and synthesized. Firstly, Diffusion and Capillary Flow-dominated membranes using chitosan and ZIF-8 were developed to separate MeOH from low-MeOH concentration feeds. Secondly, Preferential Sorption-dominated membranes using ionic liquids or ZIF-8 to selectively separate DMC from MeOH were designed and synthesized. Finally, the excellent performance of reactive pervaporation with the Diffusion and Capillary Flow-dominated membranes in the glycerol transesterification reaction with DMC was obtained.
This thesis introduces innovative pervaporation membranes guided by the "Preferential Sorption-Diffusion and Capillary Flow". These membranes enhance separation efficiency and reaction yields in equilibrium-limited processes involving MeOH and DMC. Valuable insights for chemical engineering, sustainability, and process efficiency are provided, with the potential to revolutionize industrial practices and minimize environmental impact.

Jury members :

• Prof. Patricia Luis Alconero (UCLouvain, Belgium), supervisor
• Prof.  Sandra Soares-Frazao (UCLouvain, Belgium), chairperson
• Prof.  Alexandru Vlad (UCLouvain, Belgium)
• Dr. Pieter Vandezande (VITO, Belgium)
• Prof. Wojciech Kujawski (Nicolaus Copernicus University, Poland)
• Prof. Kang Li (Imperial College London, UK)

Elia Merzari received his Ph.D. from Tokyo Institute of Technology with a thesis on the use of advanced computational fluid dynamics techniques to the simulation of flows in rod bundles. After graduation, he remained in the same institute as a Japanese Society for the Promotion of Science fellow. In 2009, he joined Argonne National Laboratory, first as a postdoctoral fellow and then as a regular staff in 2010. At Argonne, Dr. Merzari served in several roles in the Nuclear Energy Advanced modeling and simulation (NEAMS) program, for which he is currently the thermal-fluids lead. In 2019, he joined the faculty at Penn State as an associate professor. Dr. Merzari’s research relies on predictive large-scale simulations of turbulence to improve our physical understanding of complex flows and to ultimately design safer and more efficient nuclear reactors. He has received several awards related to these efforts in the area of high performance computing including: ANS Landis Young Member Engineering Achievement Award, ASME's George Westinghouse Silver Medal, and a R&D100 award.

A patterned thermoplastic film is designed for this purpose. The film makes possible a fully integrated manufacturing of joints with fracture toughness values unattained by classical adhesive joints with the possibility of fine tuning the joint properties by controlling the filling of the channels. Opposite to classical adhesive joints, this film allows for integrated manufacturing and properties tuning combined with a high fracture toughness.

Speaker : Charline VAN INNIS

Failure assessment of electronic component assemblies is crucial for the space industry in order to design reliable modules and to further enhance product lifetimes. Printed board assemblies, i.e. components soldered on printed circuit boards, are exposed to thermal cycles that are responsible for fatigue cracking in solder joints due to the mismatch in thermal expansion coefficients of the constituting elements. The problem is highly complex both to characterize exhibiting wide dispersion in the data due to inherent variability in assembly conditions and materials and also to model due to the thermal viscoplastic nature of the solder joint material and the mixed mode failure process.

The objective of this thesis is to determine the impact of material and geometry parameters on the resistance to fatigue cracking of ceramic rectangular end-capped chip component solder joints to both increase the predictive capabilities of integrity assessment schemes and to guide towards more durable designs.

A machine learning approach is used to rationalize the set of experimental results which includes some novel 3D tomography characterizations of the damage process occurring during cyclic thermal loading. Crack propagation simulations are performed using a finite element model with a traction-separation law to represent the failure process. The predictions are successfully assessed towards machine learning-processed experimental data, giving trust in the validity of the model. In particular, the high sensitivity of the component characteristic dimensions on thermal ageing reliability is properly captured. Simplified failure indicators are extracted from static simulations, allowing fast predictions but being unable to capture crack growth behaviour. Phenomenological failure power law models are identified based on experimental data and the previously developed cohesive zone model describing the fatigue cracking process. The analysis proves that the fillet and its shape play a primary role in setting the fatigue lifetime of the solder layer.

Jury members :

• Prof. Aude Simar (UCLouvain, Belgium), supervisor
• Prof. Thomas Pardoen (UCLouvain, Belgium), supervisor
• Prof.  Paul Fisette (UCLouvain, Belgium), chairperson
• Dr.  Benoît Dompierre (Cenaero, Belgium)
• Dr. Marc Bekemans (UCL Thales Alenia Space, Belgium)
• Prof. Thierry Massart (ULB, Belgium)
• Prof. Eric Charkaluk (Ecole Polytechnique, France)

Speaker : Xavier RIXHON

Parkinson's disease results in various gait impairments such as reduced gait speed, stride length and cadence, as well as a reduced level of long-range autocorrelations in series of stride durations, a subtle aspect of natural gait variability. In this thesis, the effects on gait of a walking assistance based on adaptive oscillators, naturally adapting to the user’s gait kinematics, and delivered through an active pelvis orthosis, were examined.

In the first part of this thesis, we developed model-based predictions about the loss of long-range autocorrelations in Parkinsonian patients' gait and explored the potential of restoring these using the oscillator-based walking assistance. The findings indicated that this assistance could enhance gait variability in patients, holding promise for gait rehabilitation.

In the second part, we assessed the impact of the assistance on the level of long-range autocorrelations during experiments with healthy aging subjects. The results revealed that the assistance improved gait metrics typically affected by aging, such as hip range of motion, gait speed, stride length and duration, without altering natural gait variability.

In the final part, the influence of a four-week overground gait training with the assistance on Parkinsonian patients’ gait was investigated. The results showed improvements in hip range of motion, gait speed, stride length and duration after training, with sustained effects one month later. While the level of long-range autocorrelations in the patients’ gait normalized after training, they did not retain these improvements after one month.

Jury members :

• Prof. Renaud Ronsse (UCLouvain, Belgium), supervisor
• Prof. Hervé Jeanmart (UCLouvain, Belgium), chairperson
• Prof. Frédéric Crevecoeur (UCLouvain, Belgium)
• Prof. Thierry Lejeune (UCLouvain, Belgium)
• Dr. Thibault Warlop (UCLouvain, Belgium)
• Prof. Friedl De Groote (KULeuven, Belgium)
• Prof. Olivier White (Université de Bourgogne, France)

Visio conference link : https://teams.microsoft.com/l/meetup-join/19%3ameeting_MDljMDQ2YjMtOTJlMi00MTA5LWFmMTYtZmIyOGQzMzU1NGE0%40thread.v2/0?context=%7b%22Tid%22%3a%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2c%22Oid%22%3a%2286a56c97-14f5-4133-ae40-b000941b412f%22%7d

Rapid and far-reaching mitigation strategies will be an essential part of a coherent climate change response policy. The Intergovernmental Panel on Climate Change (IPCC) namely encourages the development of carbon capture and storage (CCS) and carbon capture and utilization (CCU) technologies in order to reduce the global anthropomorphic CO2 emissions and meet the Paris Agreement objectives. In this context, research and innovation constantly seeks to improve the current techniques and develop novel promising alternatives.

This work explores a new CO2 capture and revalorization process that leads to the production of (bi-)carbonate crystals, using membrane technologies. The working principle is the following: first, the CO2 contained in industrial post-combustion flue gases is absorbed in an alkaline solvent via a membrane contactor. Then, the carbonate compound in aqueous phase is recovered using membrane distillation-crystallization, producing high-quality crystals that can finally be revalorized in the chemical industry. This thesis attempts to understand and optimize the membrane distillation-crystallization step from a technical, economic and environmental point of view. Osmotic, direct contact and vacuum membrane distillation are discussed and compared. A life cycle assessment of the overall process is performed in order to determine its environmental pertinence.

Jury members :

• Prof. Patricia Luis Alconero (UCLouvain, Belgium), supervisor
• Prof. Renaud Ronsse (UCLouvain, Belgium), chairperson
• Prof.  Tom Leyssens (UCLouvain, Belgium)
• Dr. Denis Roizard (Université Lorraine, France)
• Prof. Anne-Lise Hantson (UMons, Belgium)
• Prof. Angélique Léonard (Université de Liège, Belgium)

Link of the videoconference

In this seminar, I present strategies to design energy systems that comply with zero-emissions targets while minimizing total system costs. Design strategies are obtained by formulating mathematical optimization problems that determine the optimal selection, size, and operation of energy conversion and storage technologies that supply a given energy demand at the minimum cost. I focus on the role of energy storage, by providing insights on the competition of short- vs. long-term energy storage – here, batteries vs. hydrogen storage. The analysis covers multiple spatial scales, ranging from neighborhood-scale distributed energy systems to the national (Swiss) and European energy systems.

Speaker :

Paolo Gabrielli is a Senior Scientist at ETH Zurich, within the Institute of Energy and Process Engineering, and is currently a Visiting Investigator at Carnegie Science at Stanford University.

He studies the transition to net-zero energy systems, with a focus on the optimization and assessment of distributed energy systems, energy storage, hydrogen, and carbon supply chains. He also investigates strategies to achieve net-zero emissions in hard-to-abate sectors, with a focus on the chemical industry.

Paolo Gabrielli holds a B.Sc. and M.Sc., both in Energy and Nuclear Engineering, from the University of Bologna, and a Ph.D. from ETH Zurich, for which he was awarded the Hilti Prize 2021. He performed his M.Sc. program at UCLA with an Overseas Scholarship and his M.Sc. thesis at DTU with an Excellence Scholarship, both granted by the University of Bologna. Before joining ETH Zurich, he worked in the R&D division of General Electric Aviation and in the Renewable Energy Services practice of South Pole.

The project proved the great potential of machine learning tools and algorithms for the turbulence modeling of liquid metal flows. The new data-driven algebraic model was remarkably accurate and applicable to different flow configurations and regimes. Thanks to its robustness-oriented training strategy, the thermal turbulence closure can be combined with momentum turbulence models of different fidelity levels. The more explorative work carried out in the second order framework increased our understanding of the budget mechanisms and laid out their dependency on the Prandtl number of the fluid. Additional data, and the development of a unified methodology embracing field inversion and regression steps would further increase the performance of the augmented model and its generality.  

Jury members :

• Prof. Yann Bartosiewicz (UCLouvain, Belgium), supervisor
• Dr. Lilla Koloszar (Von Karman Institute for Fluid Dynamics, Belgium), supervisor
• Prof. Aude Simar (UCLouvain, Belgium), chairperson
• Prof.  Elia Merzari (Penn State University, USA)
• Prof. Paola Cinnella (Université Sorbonne, France)
• Prof. Matthieu Duponcheel (UCLouvain, Belgium)
• Prof. Miguel Alfonso Mendez (Von Karman Institute for Fluid Dynamics, Belgium)

Visio conference link : https://teams.microsoft.com/l/meetup-join/19%3ameeting_ZDBiOTNhZjctMzE5NS00Nzg3LWFkOTUtYzIxMzY2Y2Y0ODM4%40thread.v2/0?context=%7b%22Tid%22%3a%221677f82a-0032-424b-99e5-5fe06fa53796%22%2c%22Oid%22%3a%22916cca0c-cd2e-4edb-9007-ee7c69be6874%22%7d

John Hutchinson received his undergraduate education in engineering mechanics at Lehigh University and his graduate education in mechanical engineering at Harvard University. He joined the Harvard faculty in the School of Engineering and Applied Sciences in 1964 and is currently the Abbott and James Lawrence Professor of Engineering Emeritus. Hutchinson and his collaborators work on problems in solid mechanics concerned with engineering materials and structures. Buckling, structural stability, elasticity, plasticity, fracture, and micro-mechanics are all central in their research. Ongoing research activities are:

(1) development of a mechanics framework for assessing the durability of thermal barrier coatings for gas turbine engines,

(2) fracture mechanics of tough ductile alloys,

(3) the mechanics of thin films, coatings, and multilayers, and

(4) stability phenomena in plates, shells, and soft materials.

Further information and publications can be downloaded at  https://groups.seas.harvard.edu/hutchinson/

This brief seminar provides an tour d'horizon of an inviscid model for unsteady external aerodynamics within a two-dimensional framework. It introduces the fundamental components that form the basis of this model, illustrating how
basic vorticity elements are employed to characterize the behavior of fluid flows around solid airfoils or flexible self-propelled swimmers, enabling the calculation of both internal and external forces experienced by these entities.

Furthermore, it discusses impulse-related techniques to streamline the computational efficiency and enhance the stability of the numerical model.

Despite their potential benefits, the integrated use of renewable fuels at the European scale has been little studied. This study addresses this gap by applying a multi-regional whole-energy system optimization model, EnergyScope Multi-Cells, to develop a fossil-free European energy system by 2050. This model considers all energy sectors and several energy carriers, enabling a direct comparison of renewable fuels with competing alternatives. We analyze the strategic use of renewable and provide guidelines on their quantities for key applications such as storage, the chemical industry, and energy exchanges within Europe. Furthermore, we analyze the origin of these fuels in the different scenarios: whether they are imported or produced in Europe, and the implications for energy sovereignty.

Overall, our study provides valuable insights into the strategic use of renewable fuels in a fossil-free European energy system. The guidelines and analyses we provide can inform policymakers, industry stakeholders, and researchers in their efforts to promote sustainable and secure energy systems.

During this presentation, we will delve into the invaluable role of Computational Fluid Dynamics (CFD) simulations in assessing the fluid behaviour within an electrolysis cell. Through modeling and simulation, the goal will be to identify optimal configurations that promote electrolyte homogenization and efficient removal of gas bubbles. This, in turn, is expected to enhance the overall performance of the electrolyzer and facilitate the transition towards a greener, more sustainable energy landscape.

► Travel and accomodation

Programme:

Monday December 4th

12:30-13:15: Light sandwich lunch

13:15-13:30: Welcome address, Aude SIMAR (UCLouvain, Belgium)

13:30-13:55: In-process excavation and repair of defective FSW joints; application to space launchers, Dorick BALLAT-DURAND (ArianeGroup SAS)

13:55-14:20: Comparison of Friction Stir Welding with different fusion welding processes in joining Aluminium EN AW-6063 T6, Iurii GOLUBEV, Axel MEYER (RIFTEC GmbH, Germany)

14:20-14:45: Study of robotized Friction Melt Bonding on FSW welding cell: implementation on overlap welding of mild steel with aluminum, Mathieu LUCAS, Damien NOIZILLIER, Sandra CHEVRET (LCFC, Arts et Métiers Institute of Technology, Metz, France), Sophie RYELANDT, Aude SIMAR

14:45-15:10: High speed FSW of aluminium alloys – Results from the Albatross project, Jeroen DE BACKER (TWI, UK, University West, Sweden), Pedro SANTOS, Vivek PATEL, Irem SAPMAZ

15:10-15:35: Fatigue Performance of Refill Friction Stir Spot Welded 2219 Aluminium Alloy Joints , Matteo BERNARDI (Leuphana University, Lüneburg, Helmholtz-Zentrum, Germany), Ting CHEN, Canelo DAVID, Luciano BERGMANN, Benjamin KLUSEMANN

15:35-15:50: FSW's industrial feedback: New challenges, Landry GIRAUD (Tra-C Industrie, France), François JOSSE

15:50:16:05: AALASA project – FSW of Aluminium- Lithium alloys for space applications, Philippe DUFOUR (Sonaca, Belgium), Vivien CROES, Steven KEYZER, Philippe LEGROS, Matthieu B. LEZAACK, Yves MARCHAL, Aude SIMAR, Okan YILMAZ

16:05-16:35: Coffee break

16:35-17:00: Friction Stir Welding Operating Window for Aluminum Alloy Obtained by Temperature Measurement, Moura ABBOUD, Laurent DUBOURG (Stirweld, France), Adrien LEYGUE, Guillaume RACINEUX, Olivier KERBRAT

17:00-17:25: Microstructure evolution in friction extrusion of aluminium alloys, Lars RATH, Chang CHAN, Uceu SUHUDDIN, Benjamin KLUSEMANN (Leuphana University, Lüneburg, Helmholtz-Zentrum, Berlin,Germany)

17:25-17:50: The influence of the deposition speed during friction screw extrusion additive manufacturing of AA6060, Ton BON (University of Twente, Netherlands), Sharon STRIK, Saed SAYYAD REZAEINEJAD, Martin LUCKABAUER, Remko AKKERMAN

17:50-18:15: Multi-layer friction surfacing of aluminium alloys: microstructural and mechanical properties, Marius HOFFMANN (Leuphana University, Lüneburg, Helmholtz-Zentrum, Germany), Arne ROOS, Zina KALLIEN, Benjamin KLUSEMANN

18:15-18:40: Heterogeneities in solid-state additively manufactured 7075 aluminium alloy, Matthieu JADOT (UCLouvain, Belgium), Jishuai LI, Jichang XIE, Matthieu B. LEZAACK, Thaneshan SAPANATHAN, Mohamed RACHIK, Aude SIMAR

18:40-18:55: Investigating the role of microstructural features in plastic deformation of friction-stir deposited aluminum, Florian GIRAULT (ONERA – the French aerospace lab, Châtillon, LMS – CNRS, Ecole Polytechnique, Palaiseau, France), Louise TOUALBI, Thibaut BOUILLY, Alexandre TANGUY, Simon HALLAIS, Matthieu LEZAACK, Eric CHARKALUK

19:30-21:30: Workshop diner
(please make sure you inform in the registration googleform if you are not participating, or tell Catherine Bauwens - catherine.bauwens@uclouvain.be)

Tuesday December 5th

8:30-8:55: Optimum FSW welding parameters assessment for quasi-pure copper butt joints using external heat source: experimental and numerical investigations, R. BULACU, C. BADULESCU, Younes DEMMOUCHE (ENSTA Bretagne, France), M. IORDACHE, E. NITU, M. DHONT, M. DIAKHATE

8:55-9:20: Why is the extension of an Representative Volume Element (RVE) of the nugget zone of an FSP single track of LPBF AlSi10Mg towards an RVE of multiple tracks not straightforward? Chantal BOUFFIOUX, Olivier DEDRY, Hector SEPULVEDA, Anne MERTENS, Camille VAN DER REST, Aude SIMAR, Laurent DUCHENE, Anne-Marie HABRAKEN (ULiège, Belgium)

9:20-9:45: Simulation of the Friction Melt Bonding process using FEM and PFEM, Eduardo FERNANDEZ (ULiège, Belgium), Tianyu ZHANG, Billy-Joe BOBACH, Luc PAPELEUX, Simon FÉVRIER, Martin LACROIX, Romain BOMAN, Jean-Philippe PONTHOT

9:45-10:10: Demonstration of the ScanStir FSW web application, Henrik Blicher SCHMIDT (HBS Engineering ApS, Denmark).

10:10-10:35: Influence of uniform intermetallic thickness on weld strength in dissimilar Titanium and aluminium welds processed by Friction Melt Bonding (FMB), Sanjay C KRISHNAMURTY (UCLouvain, Belgium), Thaneshan SAPANATHAN, Aude SIMAR

10:35-11:00: Coffee break

11:00-11:15: Introduction to the FSWP conference in Coimbra in 2025, David ANDRADE, Ivan GALVAO, Dulce M. RODRIGUES (University of Coimbra, Portugal)

11:15-11:40: Fatigue life improvement using friction stir processing (FSP) of high strength aluminium alloys produced by laser powder bed fusion (L-PBF), Camille VAN DER REST, Nicolas NOTHOMB (UCLouvain, Belgium), Sophie DE RAEDEMACKER, Marie-Noëlle AVETTAND-FENOEL, Juan Guillermo SANTOS MACIAS, Lv ZHAO, Aude SIMAR

11:40-11:55: Process parameters-based coefficients for determining temperature and torque in FSW and FSSW, David ANDRADE (University of Coimbra, Portugal), Carlos LEITAO, Dulce M. RODRIGUES

11:55-12:10: Analysis of the bonding interface in FSSW of Ti-based dissimilar systems, Ivan GALVAO, Rui LEAL, Carlos LEITAO (University of Coimbra, Portugal)

12:10-12:35: Enhancing Performance of Welded Additively Manufactured Aluminium Alloy Components through Friction Stir Welding, Rafael NUNES (Belgian Welding Institute, UGent, UCLouvain, Belgium), Matthieu LEZAACK, Aude SIMAR, Koen FAES, Wim DE WAELE

12:35-13:30: Light sandwich lunch

Travel and accomodation:

Euler building, Av. Georges Lemaitre 4, Louvain-la-Neuve, Belgium

List of hotels in Louvain-la-Neuve :

• Hotel Martin's Agora City Resort Louvain-la-Neuve
• Hotel Ibis Styles Louvain-la-Neuve
• Gîte Mozaïk Louvain-la-Neuve (gîte-auberge Kaleo)
• B-Lodge

List of hotels outside Louvain-la-Neuve :

• Piano 2 Hotel
• Best Western Hôtel Wavre
• Novotel Wavre Brussels East
• Ibis Wavre Brussels East

For parking outside any hotel parking lot, it is recommended to obtain a parking sticker by sending your license plate number to Catherine Bauwens (catherine.bauwens@uclouvain.be).

The need for high-resolution 3D imaging of biological tissues is a driving force behind the development of innovative technologies. Among these technologies, microfocus computed tomography (MicroCT) stands out for its exceptional spatial resolution, user-friendliness, and cost-effectiveness. While MicroCT excels at providing non-destructive 3D views of tissue samples, it is limited to visualizing dense tissues, such as bone, that strongly interact with X-rays.

To address this limitation, researchers have developed methods to enhance the contrast of soft tissues. The approach studied and discussed in this dissertation focuses on the use of heavy atom-containing molecules, known as contrast-enhancing staining agents (CESAs). These molecules passively diffuse into an ex vivo biological tissue sample and disperse throughout the tissues based on their affinity, contributing to improved tissue contrast. This specific methodology is also called contrast-enhanced computed tomography (CECT).

Within this thesis, a series of case studies were conducted to shed light on the staining mechanisms and diffusion kinetics of both established and novel CESAs for 3D histopathology of biological tissues. The primary focus was on investigating the chemistry and interactions of these staining systems, with each case study centered on a specific tissue or organ. In the first project, we explored the potential of CECT in revealing the microstructure of healthy murine brain hemispheres, as well as in murine disease models of Alzheimer’s disease and multiple sclerosis. The second project involved screening various CESAs for the study of adipose tissue in the bone marrow and muscle. Additionally, the staining mechanism of Lugol’s iodine components with respect to biological tissues was investigated using both simplified and more complex model systems. The third project centered on studying the diffusion kinetics of different types of polyoxometalates (POMs) through the porcine aorta wall.

In summary, this thesis has provided invaluable insights into the staining kinetics and mechanisms of CESAs for biological tissues. Furthermore, it has introduced novel CESAs into various fields of CECT, paving the way for further advancements in CESAs for 3D histopathology of biological tissues using CECT.

Jury members :

• Prof. Greet Kerckhofs (UCLouvain, Belgium), supervisor
• Prof. Wim De Borggraeve (KU Leuven, Belgium), supervisor
• Prof. Elke Debroye (KU Leuven, Belgium), chairperson
• Prof. Catherine Behets (UCLouvain, Belgium)
• Prof. Mario Smet (KU Leuven, Belgium)
• Prof. Mark Grinstaff (Boston University, Boston, US)
• Dr. Nada Savic (KU Leuven, Belgium)

Two main global objectives were considered in this study, namely: i) the determination of pollution and toxicological risk of pollutants on the northwestern slope of Lake Tanganyika, and ii) the development of a treatment method of domestic and industrial wastewater by commercial membranes, including the preparation of a low-cost membrane to remove pollutants.

The determination of pollution was based on chemical analysis of organic and inorganic micropollutants, and the toxicity test by bio-testing was experimented in aquariums at the laboratory of the Hydrobiology Research Center in Uvira. The results show that the wastewater is polluted by highly toxic inorganic and organic compounds. The sources of pollution came from the reference hospital of Uvira, the penitential center of Uvira, the households, the artisanal food-processing industries, the degradation of non-recycled household waste and the physical alteration of the sedimentary rocks of the Precambrian period that form the substrates.
The real waters sampled in Uvira were filtered on 200 μm filter paper to retain large particles that can affect membrane fouling and clogging. These real waters had not undergone any other chemical pre-treatment. After the physical pretreatment, they were filtered on commercial reverse osmosis membranes of polyamide type and NF90, NF270 to remove inorganic micropollutants.

The synthetic waters were prepared in the laboratory with the specific ions under study at known concentrations. Those waters were filtered through commercial reverse osmosis membranes, as well as nanofiltration membranes (NF90 and NF270) to remove metal ions. The experimentation of commercial membranes allowed to evaluate its performance. Next, a membrane containing chitosan and the metallic organic framework ZIF-8 (i.e., CS/ZIF-8 mixed matrix membrane) was prepared at the laboratory and characterized by XRD, SEM, FTIR, angle contact, and tested in the reverse osmotic unit using the synthetic waters at different concentrations.

The results obtained show that the retention of ions by the polyamide reverse osmosis membranes is excellent, although the permeate flux is low. The retention with nanofiltration membranes depends on the feed concentration and ionic interactions at the membrane surface. Regarding the self-made CS/ZIF-8 mixed matrix membrane, it shows better retention performance for Cr3+, Pb2+, Cd2+ and Ni2+ ions in a concentrated feed solution and high-water permeability at low operating pressure. In addition, industrial scaling-up of the CS/ZIF-8 membrane is more attractive, as the manufacturing cost is low and the permeate flux high. The economic feasibility analysis shows that the investment cost is high, but energy consumption is low.

Jury members:

• Prof. Luis Alconero Patricia (UCLouvain, Belgium), supervisor
• Prof. Musibono Eyul Dieudonné (Université de Kinshasa, RDC), supervisor
• Prof. Soares-Frazao Sandra (UCLouvain, Belgium), chairperson
• Prof. Raskin Jean-Pierre (UCLouvain, Belgium)
• Prof. Figoli Alberto (Insitute on membrane Technologie, Italy)
• Prof. Buleng Njoyim Estella (University of Dschang, Cameroun)
• Prof. Vanhove Maarten (Université Hasselt, Belgium)
• Prof. Mputu Kanyinda Jean-Noël (Université de Mons, Belgium)

Visio conference link :  Visio conference link

Closing the metal fuel cycle

Research on the reduction process of iron-ore at the TU/e

The impact of climate change due to greenhouse gasses has been acknowledged and countries across the world are introducing policies to reduce these emissions. Renewable energy sources like solar and wind energy are used as an alternative to fossil fuels. However, these renewable sources with intermittency demands stable alternative: dense energy storage, like metal. Metals such as iron, are cheap and widely available, can be burnt with air to release its chemical energy. The thermal energy which is released during this process provides heat to high energy- and emission- intense industries. After combustion the generated iron oxides are captured and reduced back to iron. At Eindhoven University of Technology (TU/e) we investigate different methods to reduce combusted iron back to iron in an efficient way. An overview will be given of these activities undertaken at the TU/e and the reduction team spearheading these efforts will be introduced.

Biography: Nicole Stevens is a Doctoral Candidate at the Power and Flow group in the Mechanical Engineering Department of Eindhoven University of Technology (TU/e) under supervision of full professor Niels Deen and assistant professor Giulia Finotello. She researches the reduction of iron oxide as part of the metal fuel cycle and the potential of the whole cycle as renewable energy source.

Numerical modelling of single iron particle combustion

Iron powder is considered as a promising metal fuel since it is inherently carbon-free, recyclable, compact, cheap and widely available. To design and improve real-world iron-fuel burners, an in-depth understanding of the fundamentals underlying the combustion of single iron particles is required. Since iron burns in a heterogenous way, it was believed that no iron was lost through evaporation during the combustion process. However, our research has demonstrated that, despite the particle temperature remaining below its boiling point, a small but non-negligible mass loss occurs through evaporation. Furthermore, for iron particle combustion, it has been hypothesized that the oxidation rate of an iron droplet is the result of an interplay among three mechanisms: (1) External diffusion of O2 from the ambient gas to particle surface, (2) surface chemisorption of, and (3) internal transport of Fe and O atoms. In this study, we explore these limiting mechanisms through the utilization of various numerical methodologies, including boundary-layer resolved models, point-particle models, and molecular dynamics simulations.

Biography: Leon Thijs obtained his BSc degree in Mechanical Engineering at Eindhoven University of Technology (TU/e) in 2017. He obtained his MSc double degree in Mechanical Engineering (Power & Flow group) and Applied Physics (Fluids & Flow group) in 2020. Directly after graduation, Leon joined the Power and Flow group as a Doctoral Candidate in 2020. In this position, he is now working on model development of single metal particle combustion under the supervision of Prof. Philip de Goey, Prof. Jeroen van Oijen and Dr. XiaoCheng Mi. For his contribution to the 39^th International Symposium on Combustion he received the Distinguished Paper Award in the Solid Fuel Combustion Colloquium for the paper entitled “Resolved simulations of single iron particle combustion and the release of nano-particles”.

Application of Computational Thermodynamics to Materials Design and Process Optimization – High Temperature Thermochemistry Lab at Seoul National University

The research at the High Temperature Thermochemistry lab, Seoul National University, is mainly directed towards the development of critically evaluated thermodynamic databases for multicomponent, multiphase systems and their applications to metallurgical processes. These databases contain descriptions of thermodynamic properties of all phases within a target system. As a key developer of the well-known FactSage thermochemical software, the research group has developed comprehensive thermodynamic databases for oxide, oxyfluoride, and steel related to steel refining, refractories, continuous casting mold flux, and high alloy steels, as well as physical property databases for molten oxide and alloys derived from thermodynamic calculations. With these FactSage databases, complex chemical equilibria can be calculated for material and process design. Moreover, by combining thermodynamics and reliable kinetic expressions, process simulation models are developed for steelmaking units employing the so-called Effective Equilibrium Reaction Zone (EERZ) approach. In this seminar, an overview of these research activities will be given. 

Biography: Dr. Marie-Aline Van Ende is a Research Professor at the Department of Materials Science and Engineering, Seoul National University, Korea, since 2017, and, since 2023, a part-time Associate Professor at the department of Mechanical Engineering, Eindhoven University of Technology, The Netherlands. She obtained her bachelor and Master degrees in Chemical Engineering from Université Catholique de Louvain, Belgium. She carried out a PhD study in Materials Engineering at the Katholieke Universiteit Leuven and Université Catholique de Louvain, Belgium, and obtained her PhD degree in 2010. Until 2017, she worked as a Postdoc and Research Associate at the Department of Mining and Materials Engineering, McGill University, Canada. She has over 10 years of expertise in the development of thermodynamic databases for metallic and oxyfluoride systems for the computational thermodynamic software FactSage and in the development of industrial process simulations using FactSage.

In this presentation, LES is used to study the wake generated by AWES. Two types of wings are considered: a straight wing, modelling a reference rigid wing AWES, and a curved wing accounting for leading edge inflatable kites. Both types are modelled using an actuator line method. A wake analysis and comparison for purely circular trajectories reveals that the wake of curved wings tends to be stronger and to recover faster. This is attributed to the curved geometry of the wing and to the effects of its tips.

Then, the case of a straight wing AWES flying a realistic trajectory with reel-out and reel-in phases is simulated. Two trajectories are considered, and the number of loops for the reel-out phase is shown to influence significantly how turbulence is released in the wake.

Part 1: Nathan Klavzer

How doing some simulations can be insightful - an example in polymer composites

Have you had some finite element (i.e. numerical simulations) classes in the past and got scared or, perhaps, disgusted ?  Well, let me help you regain faith in the usefulness of simulations in your PhD/work !! I want to show you how simulations can help you find answers that you may not be able to get experimentally. But don’t worry, this won’t be a long lecture full of details about simulations… Instead, I will simply illustrate one instance where the use of simulations solved one (of my many) problems ! More precisely, I will explain how enriching a classical continuum model with strain gradient plasticity theory allowed improving failure predictions of polymer composites.
 

Part 2: Antoine Hilhorst

Fun and efficient note taking

I have been using the software "Obsidian" for note taking and I found it very useful. In a quick presentation, I want to share how I use this tool for note taking but also project management, literature review, and database building. I will also take this opportunity to remind my fellow researchers of a few useful resources.

The XDG-method is designed to obtains solutions, resp. approximations to such discontinuous problems with a high order of accuracy. Here, the fluid interface is embedded within a Cartesian background mesh. The discontinuous finite elements, defined on the background mesh are extended in a fashion so that they are capable of approximating singularities (e.g., jumps and kinks) in the pressure and the velocity field with a high order of accuracy.

This talk aims to provide a comprehensive overview of the XDG methodology, highlighting essential aspects such as stabilization techniques and the agglomeration of small cut cells. Furthermore, the discussion extends to exploring the application potential of XDG methods in areas beyond their conventional scope, inviting a broader understanding of their versatility and effectiveness in complex flow simulations.

About the Author:

Career Path:

•    2015 – now: Research group leader at the Chair of Fluid Dynamics (FDY), TU Darmstadt• responsible for multi-phase research group and software development
•    2014 – 2015: Visiting Scholar at the Department of Computational and Applied Mathematics (CAAM), Rice University
•    2013 – 2014: Research Associate at Center for Turbulence Research (CTR), Stanford University
•    2006 – 2012 Research Staff at Chair of Fluid Dynamics (FDY), TU Darmstadt (PhD Student, Postdoc)
•    2000 – 2006: Studies of Technical Mathematics, University of Innsbruck

Research interests:

•    Development of numerical methods
o    Mostly focused on extended methods (XDG)
o    Special emphasis on multiphase flows
•    High Performance Computing
o    Iterative Solvers for indefinite, unsymmetric systems
•    Application of Continuous Integration Practices for Scientific Software Development.

Syngas produced by small-scale downdraft gasification is affected by two main challenges: it has a low energy density and contains residual tar that can harmfully condense in downstream processes. Steam and oxygen injection is seen as a way to address these challenges and enhance the quality of syngas. This thesis combines numerical models and experimental campaigns to investigate their effects on two-stage downdraft gasification.

Experiments on a pilot two-stage downdraft gasifier have shown that replacing secondary air with oxygen and steam enhances the syngas Lower Heating Values (LHV) by 55%, from 4.4 to 6.8 MJ∕Nm3. Steam mainly plays the role of temperature damper to avoid excessive process temperatures, but adversely affects the LHV. Steam also shifts the syngas composition to a higher H2/CO ratio.

This higher syngas LHV translates into better engine volumetric efficiency in CHP applications and a higher flame temperature for industrial burners. Although oxygen and steam enhance the gasification efficiency, the energy required for their production more than offsets the gains, resulting in a neutral to negative net energy balance. Process integration can limit this unfavorable effect, mainly through heat recovery steam generation from the syngas sensible enthalpy.

With air, steam reduces tar production, but combining oxygen and steam yields higher amounts of Class III and IV tars. This phenomenon is attributed to a less efficient mixing of oxygen and volatiles, which a modification of the injection nozzles could solve. The amount of tar remains very low compared to most other gasification technologies.

Extending the use of oxygen and steam to the primary stage first requires a better understanding of the propagation dynamics of the "smoldering" front through the biomass bed. A numerical model of the pyrolysis zone has been built by coupling a CFD model of biomass combustion with a single-particle pyrolysis model to consider the effect of particle thermal thickness. Despite promising preliminary results, the model still requires several improvements.Future research should aim to entirely replace air with oxygen and steam, using numerical simulations to identify adequate operating conditions, followed by experimental campaigns to validate their effect. In the long term, expanding the CFD model to the complete two-stage gasifier would produce a valuable tool to simulate operating conditions and support experimental results interpretation.

Jury members :

• Prof. Hervé Jeanmart (UCLouvain, Belgium), supervisor
• Prof.  Sandra Soares-Frazao (UCLouvain, Belgium), chairperson
• Prof.  Juray De Wilde (UCLouvain, Belgium)
• Prof. Julien Blondeau (VUB, Belgium)
• Prof. Frederik Ronsse (UGent, Belgium)
• Prof. Jacobo Porteiro Fresco (Universidade de Vigo, Spain)
• Dr. Yves Ryckmans (ENGIE Laborelec, Belgium)

Visio conference link

Jury members :

• Prof. Joris Proost (UCLouvain, Belgium), supervisor
• Prof. Hervé Jeanmart (UCLouvain, Belgium), chairperson
• Prof. Alexandru Vlad (UCLouvain, Belgium)
• Prof. Juray De Wilde (UCLouvain, Belgium)
• Prof. Mitsushima Shigenori (Yokohama National University, Japan)
• Prof. Jens Oluf Jensen (Technical University of Denmark, Denmark)

Link of the videoconference https://teams.microsoft.com/l/meetup-join/19%3ameeting_ZTAyZmUxODQtNmQ4NC00NjBlLWJhZjktOGM4YjUwZmQ3ZDZj%40thread.v2/0?context=%7b%22Tid%22%3a%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2c%22Oid%22%3a%2249698e88-b375-4572-8659-9eaa42a1ebbc%22%7d

We spatial discretizations that combine standard finite difference schemes with a weighted least-squares reconstructions of the PDE solution near immersed boundaries. We also discuss the issue of "freshly cleared cells" in simulations with moving boundaries, and demonstrate a method that maintains the high-order accuracy of explicit Runge-Kutta time integrators even in the presence of moving boundaries. Finally, we demonstrate a high-performance implementation of thesediscretizations within MURPHY, a scalable software framework for 3D multiresolution grids with wavelet-based adaptivity.

The non-local interface boundary condition of the approach is obtained by approximating the non-local Steklov-Poincaré operators, which are decomposed into a few basic units under local Taylor expansions. The approximation is proved to be effective in retaining the non-local nature of the operators and is easy to implement. The convergence analysis is performed in two steps: first ignore the boundary effect when analysing the product of Steklov-Poincaré operators applied to given functions (standard analysis); next restore the ignored boundary effect. These two steps reflect the influence of the governing equation and boundary conditions respectively. Together they describe the complete non-local nature of Steklov-Poincaré operators in application to a given problem.

In addition to his academic activities, Bas de Geus is also involved in promoting cycling as a healthy and sustainable mode of transport. He is a co-founder of the Scientists 4 Cycling network (European Cycling Federation) and a member of Géri-vélo.

I would like to talk general aspects for global warming and clarifies the reason why hydrogen is selected as energy carrier for sustainable energy system using renewable energies form both basic science and real energy system viewpoints.

Prof. Shigenori Mitsushima, Director of the Advanced Chemical Energy Research Center, Yokohama National University

Speaker: Prof. Jeremy Goldman, Michigan Technological University, USA.

The Fukushima accident in 2011 exposed our limited comprehension of the intricate processes that take place during LOCA events. This research aims to address this knowledge gap by producing accurate data on the fundamental physics that govern flow dynamics and heat transfer in this context. This objective is of great interest to the research community involved in industrial numerical simulations of SFP during LOCA scenarios.
In order to achieve these goals, we have developed a numerical tool for conducting Direct Numerical Simulations (DNS) of three-dimensional natural convection within mixed domains of porous and pure fluids, featuring an internally heated solid matrix. The tool has been validated against a large set of cases, and its numerical properties have been studied.

By doing so, we perform a sensitivity analysis on the parameters that drive the physical modeling of the porous medium, providing valuable insights into the intricate dynamics of fluid flow and heat transfer in such a configuration.
The investigation extends to exploring the effects of altering rack heights relative to the bottom wall on the flow, namely on the Large-Scale Circulation (LSC) developing above the porous medium. Furthermore, the study delves into the consequences of uneven heat load distribution within the racks.
This comprehensive examination contributes valuable insights and paves the way for an enhanced understanding of LOCA phenomena.

Jury members :

• Prof. Yann Bartosiewicz (UCLouvain, Belgium), supervisor
• Dr. Pierre Ruyer (IRSN, France)
• Prof.  Aude Simar (UCLouvain, Belgium), chairperson
• Prof. Grégoire Winckelmans (UCLouvain, Belgium)
• Dr. Matthieu Duponcheel (UCLouvain, Belgium)
• Dr. Sofiane Benhamadouche (EDF, France)
• Prof. Michel Quintard (IMFT, France)

Visio conférence : https://teams.microsoft.com/l/meetup-join/19%3ameeting_M2UyNDk5YWEtMmJmYS00MTJlLWI4NWUtMjQ2MDE2ZThmMjUw%40thread.v2/0?context=%7b%22Tid%22%3a%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2c%22Oid%22%3a%226a77f5f9-28fa-41de-986f-bcb879bb0e0e%22%7d

This thesis is organized around three main pillars. The first one concerns the modeling of some of the most important phenomena in the aerothermal ablation of melting objects. We lay down general jump conditions at the gas-liquid interface taking into account all the considered phenomena via suitable constitutive laws. We then obtain compressible volume-averaged equations with appropriate closure and equations of state to model the liquid-solid phases with phase transformation.

The models are implemented in the Argo multiphysics platform developed by Cenaero which is based on a discontinuous Galerkin discretization of the conservation laws. The second and central pillar of this thesis is the extension of this available high-order framework to a compressible two-phase sharp interface solver able to preserve its accuracy while resolving the tremendous jumps across the gas-condensed phase interface. We start by improving the accuracy of a level-set method responsible for tracking the interface motion. We then adapt the spatial and temporal schemes such as to obtain an unfitted discretization of the two-phase moving interface problem we are considering.

The last part is about the verification of the implemented models and numerical methods. To do so, we select benchmark test cases assessing several aspects of the solver. We also build up a manufactured solution framework generating reference data satisfying prescribed jump conditions. Finally, we conceive an experimental setup in a cold hypersonic environment which allows us to isolate and observe the ablation mechanisms targeted in this work.

The achievements of this work lay the foundation for extensibility of the framework to models with increasing level of complexity, toward an accurate description of the ablation by melting process.

Jury members :

• Prof. Philippe Chatelain (UCLouvain, Belgium), supervisor
• Prof. Thierry Magin (von Karman Institute)
• Prof.  Paul Fisette (UCLouvain, Belgium), chairperson
• Prof.  Jean-François Remacle (UCLouvain, Belgium)
• Dr. Pierre Schrooyen (CENAERO, Belgium)
• Prof. Juray De Wilde (UCLouvain, Belgium)
• Dr. Florian Kummer (TU Darmstadt, Germany)
• Prof. Andrea Beck (University of Stuttgart, Germany)

Viso conference link : https://teams.microsoft.com/l/meetup-join/19%3ameeting_ZjJmMzVjMWQtN2EzMy00YmU5LTg4ZjgtNjE1MjYyN2Y1NTQ0%40thread.v2/0?context=%7b"Tid"%3a"7ab090d4-fa2e-4ecf-bc7c-4127b4d582ec","Oid"%3a"4d47226c-5dac-4987-8ab1-dacc8adcdca5"%7d

Sofiane Benhamadouche will start by an overview showing the wide range of Reynolds and Rayleigh numbers which might encountered in the nuclear industry and thus the need of different approaches to model turbulence. A first part will be dedicated to advanced RANS (Reynolds Averaged Navier Stokes) modeling through second moment closures for both the dynamic and the thermal fields. A second part will focus on the need of high fidelity computations, DNS (Direct Numerical Simulation) and WR-LES (Wall Resolved-Large Eddy simulation), for a better understanding of the flow and to feed coarser models such as RANS with reliable data. Both previous parts assume that the wall is fully resolved and the use of these approaches is still limited for industrial applications. A third part will then exhibit practical applications where the concept of wall-functions is needed; at least two examples will be given; RANS simulation of the upper plenum of a PWR (Pressure Water Reactor) at a Reynolds number of 10⁸ and LES of the flow through a complex mixing grid representative of the ones used in fuel assemblies. The presentation will end by mentioning two current challenges: the prediction of the vortex penetration depth in a dead-leg and natural convection along a vertical heated plate at very high Rayleigh numbers of the order of 10¹⁵.

Speaker : Dr Sofiane BENHAMADOUCHE, EDF-France

In this lecture, I will first present you in details what are the different possibilities offered by the instrument, the different optical modes and its ultimate performances. In a second part, I will try to answer your questions as best as possible so that you can start scheduling your sample preparation.

Speaker : Armand BECHE (iMMC/LACAMI)