Compressible-Flow Simulations Using a New Large-Eddy Simulation/Reynolds-Averaged Navier-Stokes Model

A new hybrid large-eddy simulation/Reynolds-averaged Navier-Stokes simulation (LES/RANS) method is presented in this work. In this approach, the resolved turbulence kinetic energy, ensemble-averaged modeled turbulence kinetic energy and turbulence frequency, and time-resolved turbulence frequency are used to form an estimate of an outer-layer turbulence length scale that is nearly Reynolds-number-independent. The ratio of this outer-layer scale with an inner-layer length scale (proportional to the wall distance) is used to construct a blending function that facilitates the shift between an unsteady RANS formulation near solid surfaces and a LES formulation away from the wall. The new model is tested through simulations of compressible flat-plate boundary layers over a wide range of Reynolds numbers and Mach 2.86 flow over a smooth compression ramp. The results show that the new model predicts mean and second-moment statistics that are in good agreement with experiment and are comparable with those obtained using an earlier model (Edwards, J. R., Choi, J-I., and Boles, J. A., Hybrid Large-Eddy/Reynolds-Averaged Navier-Stokes Simulation of a Mach-5 Compression Corner Interaction, AIAA Journal, Vol. 464, 2008, pp. 977-991.) which required a case-by-case calibration of a model constant.