THE EFFECTS OF SUCCESSIVE DISTORTIONS ON A TURBULENT BOUNDARY-LAYER IN A SUPERSONIC-FLOW

Experiments were conducted to investigate the response of a high-Reyno lds-number turbulent boundary layer in a supersonic flow to the pertur bation presented by a forward-facing ramp. Two ramps were used: one wi th sharp corners, the other with rounded corners having radii of curva ture equal to 15 initial boundary layer thicknesses. The flow was turn ed through 20 degrees in each of the compressions and expansions. Henc e, there was no net change in the flow direction over the ramps and on ly a small change in free-stream conditions due to the entropy increas e across relatively weak shocks. The two experiments gave similar resu lts. In the middle of the relaxing boundary layer, the streamwise Reyn olds stress undershot the undisturbed levels and exhibited a response similar to that observed in subsonic boundary layer flows recovering f rom an impulse of streamline curvature (Smits, Young & Bradshaw 1979b) . The turbulent shear stress vanished throughout most of the boundary layer, and an overall destruction of the turbulence production mechani sms was apparent as the boundary layer exhibited a slow recovery.