Insights on the bleed roughness effect

Boundary-layer bleed is used in the shock interaction region of supersonic inlets. When applied correctly, it stabilizes the shock system and reduces the risk of separation. However bleed can also have an adverse effect on the boundary-layer, a phenomena referred to as boundary-layer bleed roughness. Since designers need to predict the development of the boundary-layer downstream of the bleed region, there is a need to understand and model the bleed roughness effect. This paper summarizes previous work on the subject. Existing models of the phenomena are then carefully checked against data in the literature, and data obtained from new subsonic and supersonic wind-tunnel experiments. A new turbulence model, offering improved predictive capability, is proposed and tested.