MODELING SUPERSONIC INLET BOUNDARY-LAYER BLEED ROUGHNESS

Boundary-layer mass removal (bleed) through spanwise bands of holes on a surface is used to prevent or control separation in supersonic inlets. The rough wall algebraic turbulence model of Cebeci and Chang was added to both boundary-layer and Navier-Stokes analyses to simulate the overall effect of bleed on the growth of a boundary layer. Roughness values were determined for seven bleed configurations, a range of Mach numbers between 1.3-4, and bleed rates between zero and choked values. For the bleed experiments considered, the roughness was found to be a function of the fraction of the upstream boundary-layer mass flux removed. Choked bleed flow through holes at a low angle, with respect to the surface, minimized the roughness effect and gave the best improvement in the boundary-layer velocity distribution for separation control.