Modelling the Flow in a Transonic Diffuser with One Reynolds-Stress and Two Eddy-Viscosity Models

Abstract

Turbulence modeling combined with the mass averaged Navier-Stokes equations and detailed comparisons with experimental data are presented for a transonic flow in a converging diverging diffuser for two different inlet Mach numbers. Three low-Reynolds number turbulence models, which do not use the concept of the wall distance and wall normal vector calculation are adopted: a linear eddy-viscosity model, a cubic non-linear eddy-viscosity model and a non-linear Reynolds-stress model. The compressibility effects due to the mean density variations are incorporated in a subsonic pressure-based flow solver through minor modifications to the pressure velocity-coupling algorithm and by introducing the dilatation-dissipation of turbulence to the equations of the turbulent models. Grid dependency studies were conducted and detailed velocity and pressure coefficient distributions are presented in comparison with available experimental data providing also information for the boundary layer development on the diffuser walls in the region downstream the shock wave. The final results are very promising concerning the capability of the turbulence models to capture the compressibility effects in transonic flows when they are incorporated with appropriate modifications in a pressure-based flow solver.