Computational study of a supersonic base flow using LES/RANS hybrid methodology

Large-Eddy Simulation (LES)/Reynolds-Averaged Navier-Stokes (RANS) hybrid methodology is applied to the high Reynolds number supersonic axisymmetric base flow. Both the reliability and capability of the hybrid method are investigated by the comparison with the LES, Monotone Integrated Large-Eddy Simulation (MILES), RANS simulation and the experiments. The idea of LES/RANS hybrid methodology is that RANS model is used in boundary layer, and LES model is used in massively separated regions where unsteady flow structures are precisely captured. The subgrid-scale (SGS) stresses are computed using the compressible form of the Smagorinsky model while the Baldwin-Lomax (BL) model is applied to the RANS region near the body surface because of their robustness and low computational cost. The LES/RANS hybrid simulations accurately capture the physics of unsteady turbulent flows within acceptable computational cost. The reverse flow behind the base separation shows satisfactory agreement with the measurements. The base pressure distribution, which is the primary parameter from the engineering interest, is in excellent agreement with the experiment. Dependency of the value of the Smagorinsky constant to the base pressure prediction is also investigated. The results suggest that the LES/RANS hybrid methodology is a reliable tool for the prediction of wall bounded high Reynolds number flows with the lower computational cost than that of the LES and MILES approaches.