Comparison between Weak Mach Reflection and von Neumann Reflection.

Abstract

The purpose of the present paper is to compare the characteristics of the weak Mach reflection (MR) and the so-called von Neumann reflection (vNR). A series of experiments was performed to investigate both reflections. Attention is focused on the flow properties around the triple point. By measuring the location of the triple point and the angle between the incident and reflected shocks, we estimated the approximate flow properties around the triple point. The results show that, while the triple point moves along an almost straight trajectory through a wedge tip, the angles of incidence and reflection vary as the incident shock propagates. As a result, the well-known self-similarity law does not hold for both reflections. For the von Neumann reflection, the present experimental data vary almost along the trivial solution curve of the von Neumann's three-shock theory, and an asymptotic state seems to exist on this curve. In contrast, for weak Mach reflections, these data do not lie on the trivial solution curve but reveal the so-called von Neumann paradox.