The Structure of a Shock Wave Close to a Wall

Abstract

An instationary shock wave, moving inside a channel with the velocity u_s, comes into contact with the channel walls. Fig. 1 shows a sketch of the flow field of interest. With the arrival of the shock wave leading edge the quiescent gas is set in motion and is accelerated to high speeds within a distance of a few mean free paths λ₁ of the molecules. This is accompanied by a substantial rise of temperature, pressure and density in the gas. Due to the interaction of the gas molecules with the solid wall the movement of the molecules close to the wall is hindered. The retarding influence of the wall is carried into the undisturbed flow field by molecular interaction, or what is the same on a macroscopie scale, by the action of viscous forces. Near the wall this causes additional gradients in the flow variables perpendicular to the main flow direction. Where the shock wave touches the wall a shear layer develops inside the shock wave. This shear layer is the begin of the boundary layer behind the shock wave.