Investigation of oblique shock/boundary-layer bleed interaction

Abstract

The detailed flowfield characteristics in an oblique shock-wave/laminar-boundary-layer interaction with bleed were investigated. The numerical solution for the flowfield was obtained for the strong conservation-law form of the two-dimensional compressible Navier-Stokes equations using an implicit scheme. The computations mod- eled the flow in the interaction region and inside the bleed slot for an impinging oblique shock on a flat-plate boundary layer. The computed results for the streamlines and the pressure and Mach number contours inside the bleed slot indicate that the flow is choked in the slot, with a recirculation zone near the upstream slot corner. The bleed results in the interaction zone demonstrate that flow separation is controlled. The interaction length . is reduced and the downstream velocity profiles are more favorable than the separated flow results at the same shock strength without bleed. HE control of shock/boundary-layer interactions in inlets and nozzles and over vehicle surfaces is accomplished through bleed and/or blowing in the interaction zone. In the case of mixed compression supersonic inlets, the bleed system design is critical to the efficient and stable operation of the system. Hamed and Shang1 reviewed the existing experimen- tal data for shock-wave/boundary-layer interactions in super- sonic inlets and other related configurations. According to this survey, most of the experimental measurements in mixed compression supersonic inlets consisted of total pressure re- covery surveys at the engine face and static pressure distri- butions over the inner surfaces. In the few cases involving velocity profile measurements,2-3 the latter were obtained up- stream and downstream of the interactions. Comparisons of internal flow computational results3'5 with the experimental measurements in supersonic inlets2-3 revealed reasonable agreement between the computed and measured surface pres- sures upstream of the ramp bleed. However, discrepancies in the predicted shock locations and velocity profiles were ob- served downstream of shock/boundary-layer interactions with bleed. There is enough experimental evidence6'11 to indicate that local bleed can control flow separation in shock-wave/bound- ary-layer interactions. There are disagreements,1 however, among the different experimental studies regarding the effects of bleed hole size,7-8 and the location of the bleed holes in relation to the shock.6-9'11 The experimental data in these studies are not sufficient, however, to resolve these discrep- ancies. Strike and Rippy9 measured the surface pressure in the interaction zone of an oblique shock wave impinging a tur- bulent boundary layer over a flat plate, with suction. They determined that less suction is required to control separation, when applied upstream of the shock. Seebaugh and Childs11 investigated experimentally the axisymmetric flow in the in- teraction region of the boundary layer inside a duct. Contrary to the conclusions of Strike and Rippy,9 suction within the