An experimental investigation of the interaction between shock waves and boundary layers

Abstract

An account is given of an investigation into the interaction between the boundary layer on a flat plate and a shock wave produced either externally, by a wedge in the supersonic mainstream, or from within the boundary layer, by a wedge held in contact with the plate. A wide range of free-stream Mach numbers, boundary-layer Reynolds numbers, and shock strengths has been covered, shock strength being defined as the ratio of the static pressure downstream of the shock to the static pressure upstream of it. Variations in these parameters can have large effects on the interaction, and there are also large differences between cases with externally generated shocks and cases where the shock is generated from within the boundary layer. The investigation has thrown light on the physical mechanisms involved. It is found that many of the major features of the interaction arise because the boundary layer separates from the surface ahead of the shock wave.The conditions under which separation occurs and the behaviour of the separated boundary layer thus have important effects, in terms of which, for example, the differences between the interactions observed with laminar and with turbulent boundary layers may be explained.