Fluid mechanics

IMMC

The institute is active in research projects involving advanced numerical simulations for turbulent and vortical flows, aerodynamics, thermal-hydraulics, heat transfer, granular flows, multi-phase flows, reactive flows, flows in porous media, buoyancy driven flows with evaporation, atmospheric boundary layer flows, compressible flows, flows with surface ablation, etc. This also includes the development of numerical methods and of research codes for incompressible, weakly compressible and highly compressible flows, together with their deployment on high performance computing (HPC) infrastructures; also in collaboration with research groups from other universities and research centers.

We combine this computational expertise with experimental facilities to validate numerical models or for specific experimental projects.

Applications are in the fields of aerospace and aeronautical engineering, wind energy, bio-inspired locomotion and biomechanics, nuclear thermal-hydraulics, combustion, energy systems, ejector technology; and complex flows in general.

Coherence in chaos

The flow in the mixing chamber of a supersonic ejector generates two mixing layers between the driving supersonic flow and the entrained subsonic flow. It is those highly turbulent mixing layers that are responsible for the entrainment. The flow was simulated using the Argo code of Cenaero, together with our newly developed wall model validated for subsonic and supersonic flows (to appear in J. Fluid Mechanics). The image shows the density gradient magnitude integrated across the channel width ; which mimics an experimental Schlieren photograph. It reveals the presence of large coherent structures amidst the chaos of turbulence.

Dancing vortices

Snapshot of an instantaneous vorticity field for a longitudinally oscillating cylinder in a flow at Re_D = 500. The simulation has been performed using a weak coupling between a near wall Eulerian solver and a Vortex Particle Mesh method developed by Philippe Billuart during his PhD thesis (see J. Comput. Phys. 473 (2023) 111726), and then further improved with Youri Marchal to handle cases with moving bodies.

Kites: from kid’s play to green energy

Airborne wind energy systems gather energy from the wind using a kite (rigid or soft wing) that pulls on a cable. The cable is connected to the ground and unwinds from a drum, that drives a generator. When the pulling phase ends, the wing comes back, to rewind the cable, and the cycle starts again. This picture shows the vorticity in the wake of such a wing flying a four-loop trajectory. Here it starts the second loop. Flying this trajectory creates turbulence bundles in the wake. Studying the wake is important to understand the interaction with other energy gathering devices.

The swirl of air behind a wind turbine

This image depicts the vorticity magnitude in the wake of a large wind turbine operating in realistic turbulent wind conditions. Each blade produces a vortex tube that is shed from its tip, giving rise to a near wake characterized by a helicoidal configuration. Further downstream, the vortex tubes start to break down under the influence of the ambient wind turbulence, resulting in a chaotic flow. As a consequence, any turbine placed downstream would experience a slower but more turbulent wind.This picture is the result of a Large Eddy Simulation that ran on 4096 cores for 96 hours.

Experiment of gravity flashing in a nuclear spent fuel

Temperature field and flame topology in spray combustion of biodiesel

Snapshot of the temperature field and flame topology in spray combustion of biodiesel

Large Eddy Simulation of a four-blade helicopter rotor at low advance ratio

Large Eddy Simulation of a four-blade helicopter rotor at low advance ratio, performed using a Vortex Particle-Mesh (VPM) method. The illustration shows a volume rendering of the vorticity magnitude.