NUMERICAL STUDIES ON LIP SHOCK FLOW BEHAVIORS OVER BACKWARD FACING SHARP EDGE STEP WITH HYBRID RANS-LES

In the present research, a 2D numerical model is developed to investigate supersonic turbulent fluid flow over a backward facing sharp edge step by using hybrid RANS-LES model. It pertains to the Spalart-Allmaras model involving a viscosity-like variable (ṽ). The model also takes into account the additional important factors like production, diffusion and destruction terms above and beyond the very common aspects related to the present research problem. The numerical simulations are performed using the stated turbulence model with the inflow free stream Mach number of 2.5 corresponding to free stream pressure and velocity of 15350 N/m2 and 651.9 m/s2, respectively. The simulation predictions are compared with the corresponding experimental results existing in the literature. The hybrid RANS-LES model gives fairly better and consistent results throughout the entire flow region and hence, it is used for all further studies. It is also observed that the sudden viscous layer separation is the main cause of the shock generations. Furthermore, the uneven pressure recovery is because of the sudden expansion flow over the sharp edge step. And also, the sudden expansion flow increases the shock intensity which results in uneven flow characteristics. Certainly, the present study is very much advantageous to realize the flow behaviors over any kind of backward facing sharp edge steps.