A COMPARISON OF 2 DYNAMIC SUBGRID CLOSURE METHODS FOR TURBULENT THERMAL-CONVECTION

Two dynamic subgrid-scale (SGS) closure methods for turbulent thermal convection are described. The first method assumes the dissipation rat e equals the SGS energy production rate that includes a troublesome bu oyancy term, while the second method avoids this complication with a s implifying scale analysis. Tests with large-eddy simulations (LES) of thermal convection reveal that the second method is computationally ef ficient, and produces results agreeing with direct numerical simulatio n (DNS) data, as well as values predicted by the inertial subrange the ory. Within the LES, the SGS representation is locally and dynamically adjusted to match the statistical structure of the smallest resolvabl e eddies.