DEVELOPMENT OF A LOCAL SUBGRID DIFFUSIVITY MODEL FOR LARGE-EDDY SIMULATION OF BUOYANCY-DRIVEN FLOWS: APPLICATION TO A SQUARE DIFFERENTIALLY HEATED CAVITY

Abstract

We present a local subgrid diffusivity model for the large-eddy simulation of natural-convection flows in cavities. This model, which does not make use of the Reynolds analogy with a constant subgrid Prandtl number, computes the subgrid diffusivity independently from the subgrid viscosity along the lines of the mixed scale model for eddy viscosity. First, an a-priori test is performed from a direct numerical simulation (DNS) approach in order to compare the respective effects of the subgrid viscosity model and that introduced by the QUICK scheme used to discretize the convective terms in the momentum equations. Then the subgrid diffusivity model is applied to the case of a two-dimensional square cavity filled with air for a Rayleigh number of 5 2 10 10 . Comparisons with DNS reference results demonstrate significant improvements in capturing the general pattern of the flow and particularly in predicting the transition to turbulence in the boundary layers as compared with Reynolds analogy results. The influence of subgrid diffusivity on the local heat transfer is also examined.