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HYBRID RANS-LES MODELING FOR NON-EQUILIBRIUM TURBULENT FLOWS

Bruno Chaouat
Department of Computational Fluid Dynamics and Aeroacoustics, ONERA BP 72 - 92322 Chatillon cedex, France

Roland Schiestel
IRPHE, UMR 6594 CNRS, 49 rue Frédéric Joliot-Curie - B.P. 146 -13 384 Marseille Cedex 13, France

Abstract

The partially integrated transport modeling (PITM) method for subgrid turbulence quantities viewed as a continuous approach of hybrid RANS/LES methods with seamless coupling between the two extreme limits that are the full statistical and direct numerical simulation depending on the spectral cutoff location is considered (Schiestel and Dejoan, 2005). In this framework, the PITM version based on the transport equations for the turbulent stresses together with the dissipation rate equation proposed recently (Chaouat and Schiestel, 2005) is now developed in a more general formulation based on an accurate energy spectrum E(κ) valid for both large and small eddy ranges and that allows to calibrate more accurately the csgs∈2 function used in the transport equation. The model is here proposed in an extended approach that can be applied to a larger range of flows by considering the turbulence length scale Lε = k3/2/(∈sgs + ε<) built by means of the total turbulent energy k and the total dissipation rate including the subgrid zone dissipation sgs and the resolved part of the dissipation rate <. The present model is first tested on the decay of homogeneous isotropic turbulence referring to the experiment of Comte-Bellot and Corrsin. Then, initial perturbed spectra E(κ) with a peak or a defect of energy are considered for analyzing the model capabilities in non-equilibrium flow situations. The second test case chosen is the well known fully turbulent channel flow that allows to assess the performance of the model in non homogeneous flows, and especially, its capacity to reproduce the flow anisotropy.