Investigation of Negative Surface Curvature Effects in Axisymmetric Shock/Boundary-Layer Interaction

Abstract

The shock/boundary-layer interactions (SBLIs) generated by a negatively curved compression ramp are investigated. The ramp was mounted to the inner surface of a semicircular hollow cylinder, along which a turbulent boundary layer developed. Complementary experimental and computational investigations of the resulting SBLI are performed for ramp angles of 16, 20, and 24 deg at a nominal freestream Mach number of 2.5. Comparisons are made to planar cases with the same ramp angles to elucidate the influence of negative curvature on the separation size and structure. Measurements at the wall show that the negative curvature substantially increases the separation size as compared to the corresponding planar interactions. Off-body investigations reveal the focusing of shock waves originating along the circumference near the model centerline, which causes an elevation of the backpressure ratio beyond the two-dimensional limit. A constriction parameter is introduced to quantify the magnitude of this shock-strengthening effect. An area contraction mechanism results in a larger streamwise adverse pressure gradient downstream of the ramp leading edge and a reduction in outflow area that additionally inflate the negatively curved separations.