Assessment of VMS-LES and hybrid RANS VMS-LES models

Turbulent flows around bluff bodies at sub- and supercritical Reynolds numbers are simulated through a Variational Multiscale (VMS) Large Eddy Simulation (LES) model and a hybrid RANS/VMS-LES model. In VMS-LES, the separation between the largest and the smallest resolved scales is obtained through a variational projection operator and finite-volume cell agglomeration. Eddy-viscosity models are used to account for the effects of the unresolved scales. In the VMS approach, they are only added to the smallest resolved ones. We use a hybrid RANS/LES approach with a wall law for the simulation of supercritical turbulent flows. A smooth blending function allows a progressive switch from LES to RANS to be obtained, depending on the values of a blending parameter. The assessment proposed relies on the simulation of a series of flows for which experiments are available. They involve subcritical flows around a circular cylinder at Reynolds numbers (Re) 3900, 10000, 20000, and around a sphere at Reynolds numbers 10000, 50000, and supercritical flows around a circular cylinder (Re=140000, 500000, 1 million, 2 million) and a sphere (Re=400000)