Section: New Results

Turbulence models

Participants : Alain Dervieux, Bruno Koobus [University of Montpellier 2] , Carine Moussaed [University of Montpellier 2] , Maria-Vittoria Salvetti [University of Pisa] , Stephen Wornom [Lemma] , Marianna Braza [IMF-Toulouse] .

Large Eddy Simulation, Variational Multi-scale, hybrid models, unstructured meshes, vortex shedding

The purpose of our works in hybrid RANS/LES is to develop new approaches for industrial applications of LES-based analyses. This year, a lot of experiments have validated the dynamic version of our VMS-LES. The quality of simulations is either comparable to non-dynamic, or better. In the foreseen applications (aeronautics, hydraulics), the Reynolds number can be as high as several tenth millions, a far too large number for pure LES models. However, certain regions in the flow can be much 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. The french-italian team is working on a novel type of hybrid model between the VMS-LES model and a $k-\epsilon$ one. The team has this year concentrated on the shift between the RANS boundary region and the VLES boundary one. This is also the problematic on the IDDES studies. We are working on propositions relying not only on the value of the RANS viscosity but also on its gradient. A paper is in preparation on this subject.