Large Eddy Simulation of Turbulent Thermal Convection Using Different Subgrid-Scale Models

We present a comparison of large eddy simulations of turbulent convection in a cuboidal Rayleigh-Benard cell. The LES are performed with the dynamic Smagorinsky model in the momentum equation and with the subgrid scale heat transport model by Peng and Davidson [5] in the energy equation. Additionally, LES were conducted with a dynamic scale similarity model used in the momentum and in the energy equation. It was found that in contrast to the scale similarity model, the dynamic Smagorinsky model occasionally produces unphysical temperature values which must be filtered out. Their number can be reduced by increasing the filter ratio in the dynamic procedure. On the other hand, the Smagorinsky model shows a log-like dependency on the filter width ratio for all compared quantities, with the best agreement to DNS with respect to the predicted Nusselt number and SGS heat fluxes for the smallest considered filter width ratio.