Evaluation of turbulence models for flow with shock waves in a transonic diffuser

In this work, five turbulence models (k-epsilon, k-omega, SST k-omega, SA, and SAS) are evaluated for turbulent flow in a transonic diffuser used in experimental tests to generate shock waves. The models were employed within the RANS framework. Transient simulations were performed in two-dimensional computational domains for pressure ratios rp = 0.82 and rp = 0.72 using ANSYS Fluent R16.2. Sutherland's law was applied for temperature-dependent viscosity. The results were compared with experimental data for pressure, velocity, and Mach number. For pressure, the SAS model yielded a global average error of 2.62%. In the flow separation region on the upper wall of the diffuser (at the extremities of the shock front), all five models showed significant deviations from the experimental velocity data in certain regions. Regarding the Mach number, the models predicted different shock-front positions. For the maximum Mach number at the shock front, the SAS model produced errors of 0.162% (rp = 0.82) and 11.821% (rp = 0.72), respectively.