Formation of the Mach-type reflection of shock waves

The paper presents the results of experiments on the formation of the quasi-stationary Mach reflection of shock waves. The measurements were performed in a shock tube under rarefied conditions, in the vicinity of the leading edge of the reflecting wedge. The reflected shock in this region is strongly curved and moves slower than the planar shock of the same intensity. The point of reflection moves, therefore, initially along the wedge surface, and detaches from it around 100 mean free paths from the leading edge. A qualitative model of the phenomenon is also presented. It implies that the classical von Neumann's conditions for the Mach reflection are applicable only to strong shocks, when the flow behind the reflected shock is supersonic with respect to the triple point.