Analysis of mesh-independent subfilter-scale models for turbulent flows

Traditional Large-Eddy Simulation (LES) provides good results on standard benchmark turbulent flows, but engineering applications involving more complex geometries are restricted. This is mainly due to the physical hypotheses of homogeneity, isotropy, or local equilibrium of the subgrid-scale (SGS) models, which are questionable in more realistic configurations. It appears essential to qualify the built-in filters of LES models before performing coarse mesh computations. By using filtering length larger than the mesh size an analysis in the spectral space of mesh-independent Smagorinsky and Schumann models is presented. The forms of the associated built-in filters are identified, and control of the filter length through the SGS model is done. Finally the asymptotic behaviour of the filter is found to be independent of the discretization scheme.