Stabilization of a Mach 5.92 Boundary Layer by Two-Dimensional Finite-Height Roughness

摘要

In this technical note we present numerical results on the stability of a Mach 5.92 flow over a flat plate to wall blowing-suction with the effect of 2-D finite-height roughness. Four cases of numerical simulations are conducted with the roughness locating upstream or downstream of the synchronization point. The results indicate that roughness location plays an important role in the developments of mode S excited by the blowing-suction slot. Mode S is destabilized only when the roughness element is located in the close upstream region of the synchronization point. On the other hand, when the roughness element is downstream of the synchronization point mode S is stabilized. In addition, surface roughness only has local effects on the steady base flow and the stability characteristics. The relationship between the roughness location and the synchronization point suggests that a possible way to delay boundary-layer transition by putting the roughness element downstream of the synchronization point is feasible. The current study also provides a possible explanation for the roughness-induced transition delay. To understand the flow physics behind the current findings further systematic studies are needed.