Effect of surface properties on shock wave reflection

Abstract

In the reflection of shock waves off a surface von Neumann’s theory assumes compressible and inviscid flow. It also assumes the reflecting surface to be perfectly smooth, nonporous, and adiabatic. It is found to be accurate for a wide range of regular reflection patterns and limited to very strong shocks in the case of Mach reflection. However experiments have shown that regular reflection persists beyond the theoretical limit. It has been postulated that this is due to the development of a viscous boundary layer behind the reflection point, an explanation now well accepted. However, the assumption of an adiabatic wall has persisted over many years. An experiment has been devised where two inclined surfaces on either side of a symmetry plane and impacted by a propagating shock wave normal to the plane would show any differences in reflection behaviour, if they were equally smooth but of different conductivities. Tests were conducted at incident shock Mach numbers from 1.30 to 1.59, and shock incidence angles of 20 to 55 degrees with a copper surface on one side and a glass surface on the other. Detectable differences in reflection geometry were established in most cases, indicating a possible small influence on reflection patterns.