The Second-generation Louvain-la-Neuve Ice-ocean Model (SLIM) project objective is to develop a multi-scale model of the marine part of the hydrosphere (World Ocean, shelf areas, estuaries, tidal rivers) for carrying out climatic and environmental studies. It is currently extended to the atmosphere. Traditional ocean models are based on finite difference methods on structured grids. These models often work on uniform grids, which implies that the resolution is increased in a global way: reducing by two the mesh size of a model leads to an increase in the computational cost by a factor of 16.
In our model the governing equations are solved on an unstructured mesh. Unstructured meshes enable an accurate representation of coastlines and islands and allow one to avoid singularities associated with the poles in geographic coordinates. However, their main advantage is their ability to adjust the resolution when and where it is actually needed to increase the range of resolved scales. They can be refined in the areas of interest, or where the more demanding dynamics requires a finer resolution, allowing for modeling contrasting physical phenomena.
The SLIM model relies on the discontinuous Galerkin (DG) method. Among the methods based upon unstructured grids, the DG method offers several favorable features such as high-order accuracy, excellent parallel scaling and an efficient treatment of convective terms.
Developing and using ocean models based on unstructured grids is a recent topic, although numerical tools such as unstructured meshes and finite elements have been used for a while in the world of mechanical engineering. Therefore, a transfer of knowledge from the latter domain to geophysical fluid flow modeling is needed. The SLIM team, with members in both the mechanical engineering and geophysics communities, offers an excellent environment to achieved the aforementioned knowledge transfer.
The SLIM model make it possible to simulate previously inaccessible ranges of scales in the presence of complex geometry, from regional processes such as tides and pollutant transport in shelf seas to the global scale prediction of the evolution of oceanic currents. In addition, it is believed that SLIM will be ideal for modeling phenomena taking place in the land-sea continuum.
