Area Change Effects on Shock Wave Propagation

Introduction

When a planar shock wave propagating down a channel encounters a decrease in cross-sectional area, not only is the shock strengthened but the shock shape and post-shock flow are disturbed. The current research investigates how various area reduction profiles affect the shock strength and shape, as well as the uniformity of the post-shock flow for planar shocks. Bird [1] and Russell [2] investigated experimentally the effects of wall shaping and strengthening by convergence respectively using strong incident shock waves; however the current study looks at relatively low Mach numbers of 1 < M < 2. By optimising the wall shape an area reduction can be used to increase the strength of a shock significantly without compromising on the quality of the post-shock flow, which is of particular importance in the design of experimental shock tube testing. More importantly, by analysing different profiles using numerical studies, the technique could then potentially be generalized to examine to what extent a shock shape may be purposefully manipulated to a required profile by suitable wall shaping. In order to provide a comprehensive study of the topic, numerical, analytical and experimental analyses are conducted. A comparison of computational fluid dynamic (CFD) simulations and Milton’s corrected ray-shock theory [3] is examined in detail.