Growth induced by multiple shock waves normally incident on plane gaseous interfaces

Abstract

Experiments to measure the visual thickness of the mixing region produced by shock waves incident on continous and discontinous interfaces between gases of different densities have been carried out in a new vertical shock tube. The generation of vortical structures by shock-wave boundary layer interaction at the interface is observed and the need for experimental methods to distinguish the effects of resulting jets on the walls and windows of the shock tube is emphasized. Initially thick interfaces, smoothed by molecular diffusion, exhibit growth after being perturbed by acoustic noise induced during wave reverberation. Thin interfaces, whose perturbations are introduced by the rupture of the supporting plastic membrane, have a more rapid initial growth but the late time growth is comparable to that of the thicker interfaces. In both cases the rate of increase of the thickness of the interfaces is an order of magnitude less than reported by previous investigators.