An Experimental Study of Unsteady Separated Shock Wave / Boundary Layer Interactions

Abstract

An experimental investigation of the unsteady interaction between a turbulent boundary layer and a normal shock wave of strength M1 = 1:4 subject to periodic forcing in a parallel walled duct has been conducted. Emphasis has been placed on the mechanism by which changes in the global ∞ow fleld in∞uence the local interaction structure. Static pressure measurements and high speed Schlieren images of the unsteady interaction have been obtained. The pressure rise across the interaction and the appearance of the local SBLI structure have been observed to vary during the cycle of periodic shock wave motion. The magnitude of the pressure rise across the interaction is found to be related to the relative Mach number of the unsteady shock wave as it undergoes periodic motion. Variations in the upstream in∞uence of the interaction are sensitive to the magnitude and direction of shock wave velocity and acceleration and it is proposed that a viscous lag exists between the point of boundary layer separation and the shock wave position. Further work exploring the implications of these flndings is proposed, including studies of the variation in position of the points of boundary layer separation and reattachment.