NEW TRENDS IN LARGE-EDDY SIMULATIONS OF TURBULENCE

The paper presents large-eddy simulation (LES) formalism, along with t he various subgrid-scale models developed since Smagorinsky's model. W e show how Kraichnan's spectral eddy viscosity may be implemented in p hysical space, yielding the structure-function model. Recent developme nts of this model that allow the eddy viscosity to be inhibited in tra nsitional regions are discussed. We present a dynamic procedure, where a double filtering allows one to dynamically determine the subgrid-sc ale model constants. The importance of backscatter effects is discusse d. Alternatives to the eddy-viscosity assumption, such as scale-simila rity models, are considered. Pseudo-direct simulations in which numeri cal diffusion replaces subgrid transfers are mentioned. Various applic ations of LES to incompressible and compressible turbulent flows are g iven, with an emphasis on the generation of coherent vortices.