Direct testing of subgrid scale models in large-eddy simulation of a non-isothermal turbulent jet

A comparative assessment of subgrid models of compressible large-eddy simulations is performed for a temporally evolving heated round jet at a low Mach number. Initially, the temperature difference with respect to the ambient is chosen according to the one at the nozzle exit of a typical aircraft engine. Subgrid modelling in both the momentum and the energy equations is then necessary to close the problem. As basic models, we have considered the compressible versions of the Smagorinsky model, the mixed-scale model (which can be defined as a dynamic-type model) and the similarity model. The first two models are also supplemented with the similarity model or/and a selective function. Large-eddy simulations (LES) results are compared with those obtained from a direct numerical simulation (DNS). Thus to allow correspondence between DNS and LES the Reynolds number, in the present study, is still not very high and equal to 500. Among the cases investigated the hybrid Smagorinsky model (linear combination of the Smagorinsky model and the similarity model) displays the best performances, especially when dealing with the turbulent stresses and the turbulent heat flux.