A zonal RANS-LES method for compressible flows

A zonal Reynolds-averaged Navier-Stokes (RANS) - large-eddy simulation (LES) method for compressible flow problems is presented and applied to generic flow problems. The quality of the method is shown by comparing zonal RANS-LES results, pure LES, pure RANS, and direct numerical simulation (DNS) data. For the transition from the RANS to the LES regime the zonal RANS-LES approach uses a synthetic eddy method combined with control planes downstream of the embedded LES interface. This combined approach reduces the RANS-to-LES transition length to less than three boundary-layer thicknesses. At the embedded LES outflow interface a reconstruction of the turbulent eddy viscosity ensures a smooth LES-to-RANS transition. The numerical scheme of the zonal RANS-LES method is validated for compressible zero-pressure gradient boundary-layer flow and then applied to the fundamental problem of a shock-wave turbulent boundary-layer interaction (SWBLI). For both problems, a smooth transition of mean flow quantities from the RANS to the LES regime was achieved and the low frequency pressure signals were transferred without spurious disturbances from the LES to the RANS domain. For the SWBLI case the time- and spanwise averaged pressure, wall-shear stress, and Reynolds-stress distributions agree well with the pure LES and DNS reference data. This zonal method can be directly extended to more intricate flow problems. (C) 2012 Elsevier Ltd. All rights reserved.