Shock Wave Reflection Off Convex Cylindrical Surfaces

Introduction

In spite of considerable research effort in past decades, the reflection of shock waves off convex cylindrical surfaces still poses a number of unanswered questions. For a given shock Mach number M _S , the reflection pattern changes from regular to irregular at a certain wall angle Θ _w . If one determines this transition angle by visual inspection of the reflection pattern and defines it as the location of the first occurrence of a visible Mach stem, one typically arrives at wall angle values lower than the one found in the pseudo-steady case for a straight wedge at the same Mach number [1]. This would indicate that the regular reflection pattern is maintained longer on the cylindrical surface compared to the straight wedge case. Numerical simulations, on the other hand, suggest that the transition occurs at the same wall angle as for the straight wedge. If this were the case, the transition would be governed by the local wall angle and would not be influenced by the preceding history of the reflection. Furthermore, the delayed transition observed experimentally would then have to be explained as a consequence of insufficient spatial resolution of the optical records used to classify the type of reflection: If the Mach stem is too small to be optically resolved, the reflection pattern will remain to appear regular beyond the transition angle predicted by the theory for straight walls.