Effect of Inlet Mach Number on Shock-Boundary Layer Interactions in a Supersonic Turbine Cascade

Abstract

In this work, we perform large eddy simulations to assess the effects of inlet Mach number on shock-boundary layer interactions (SBLIs) in a supersonic turbine cascade at Reynolds number Re = 395,000, based on the axial chord and inlet velocity. Three inlet Mach numbers are considered being Ma = 1.85, 2.00 and 2.15. A higher Mach number leads to a stronger leading edge bow shock that, in turn, generates a more inclined oblique shock, resulting in a downstream displacement of the SBLI region on both sides of the airfoil. A consequence of these topological changes is the increase of the suction side separation bubble with the inlet Mach number. This effect is less pronounced on the pressure side, where the recirculation regions have similar length scales. An analysis of the mean flow quantities on the suction side shows a higher pressure jump across the incident shock for a lower inlet Mach number. On the other hand, the opposite is true for the pressure side. Finally, the unsteadiness of the SBLIs is investigated using spectral analysis for all cases. The results indicate that, as the inlet Mach number increases, the low-frequency regions with high-amplitude spectral energy move downstream in the axial direction, and the SBLI systems excite even lower frequencies when these are scaled by the axial chord and inlet velocity.