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Section: New Results

Turbulence models

Participants : Emmanuelle Itam [University Montpellier II] , Alain Dervieux, Bruno Koobus, Carine Moussaed [University Montpellier II] , Maria-Vittoria Salvetti [University of Pisa] , Stephen Wornom, Bruno Sainte-Rose [Lemma] .

The purpose of our work in hybrid RANS/LES is to develop new approaches for industrial applications of LES-based analyses. This year, many experiments have validated the dynamic version of our VMS-LES. The quality of simulations is either comparable to non-dynamic, or better. In the applications targetted (aeronautics, hydraulics), the Reynolds number can be as high as several tenth millions, far too high for pure LES models. However, certain regions in the flow can be better predicted with LES than with usual statistical RANS (Reynolds averaged Navier-Stokes) models. These are mainly vortical separated regions as assumed in one of the most popular hybrid model, the hybrid Detached Eddy Simulation model. Here, “hybrid” means that a blending is applied between LES and RANS. An important difference between a real life flow and a wind tunnel or basin is that the turbulence of the flow upstream of each body is not well known. This year, we have started the study of multiple-body flows. A typical case is the interaction between two parallel cylinders, one being in the wake of the other. A recent workshop showed the rather disastrous predictions of LES models. Most hybrid models behave better, mainly for the first cylinder. We are progressively extending and validating our VMS-LES model and our hybrid ones ([11] ).