RANS/LES coupling for unsteady turbulent flow simulation at high Reynolds number on coarse meshes

Industrial flow simulation usually concerns high Reynolds number and wall-bounded configuration. Unfortunately, large-eddy simulation (even with wall models) needs a great wall refinement to handle this kind of flows. This increases drastically the simulation computational cost up to become prohibitive. This study has two major objectives. To begin with, main drawbacks of large-eddy simulation for isothermal situation with usual wall models in coarse grids for high friction Reynolds number up to 2 × 104 in a plane channel flow configuration are highlighted using the Trio_U code developed at CEA Grenoble. Then, two strategies to improve the simulations results are proposed. First, a sophisticated wall model (called TBLE wall model) was tested and provided some improved results in low Reynolds number cases. However, shortcomings observed for large-eddy simulations with usual wall models seem to continue with the use of TBLE wall model. Then, a RANS/LES coupling approach relying on a forcing term was investigated and provided some promising results.