## LARGE EDDY SIMULATION OF A COMPRESSIBLE MIXING LAYER WITH A TIME SELF-ADAPTIVE MULTILEVEL METHOD
## 要約Large-Eddy Simulation (LES) allows to reduce the computational costs in the numerical simulation of turbulent flows in comparison with Direct Numerical Simulation (DNS). This reduction is obtained by a scale separation, the largest ones being directly resolved, while the smallest ones (subgrid scales) are modeled. Nevertheless, usual eddy-viscosity subgrid models have been developed in the framework of homogeneous isotropic turbulence, and are so not able to take into account in a proper way the presence of inhomogeneous subgrid scales, or backscatter. That is why LES still require the use of fine computational grids, and thus a large amount of CPU ressources. A multilevel method applied to LES is introduced here to reduce the CPU times. Flow variables are decomposed into several frequency bands, each band being associated to a computational grid in physical space. The high-frequency deterministic information from the finest levels can then directly be used on the coarse ones to get an accurate evaluation of the subgrid model, as in deconvolution-like approaches (Stoltz and Adams, 1999, Domaradzki and Yee, 2000). CPU time saving is obtained by performing the main part of the simulation on the coarse levels by freezing the smallest resolved scales (Quasi-Static approximation-Dubois |

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