Numerical Modeling of the Turbulent Supersonic Flow Over a Backward Facing Step

The flow over a backward facing step is a classic problem in applied aerodynamics. Among many other applications, backward facing steps are often used for ignition and stabilization of the flame in a scramjet engine. In this study, the steady two-dimensional viscous supersonic turbulent flow over a backward facing step was calculated using FLUENT. The one-equation Spalart and Allmaras turbulence model was employed for the turbulent flow simulation. The free stream Mach number was 2. The simulated flow field is in good qualitative agreement with flow visualizations, pressure and temperature measurements and theoretical predictions. The boundary layer ahead of the step turns through the right angle over the corner. Then a separation occurs below the corner on the step wall. The numerical results indicate that the separation point is positioned on the step face, below the corner. The overexpansion at the corner is balanced by a lip-shock. This phenomenon was observed in experimental measurements, in flow visualizations and is also obtained in the present numerical calculation.