New Findings on the Shock Reflection from Wedges with Small Concave Tips

Planar shock reflection from straight wedges and wedges with small concave tips is considered. It is demonstrated that, in shock tube experiments for a certain wedge angle and incident shock Mach number, the resulting reflection is of irregular type in the presence of a small concave tip with an arc radius as small as 4 mm while a straight wedge with the same wedge angle produces a regular reflection. In the numerical experiments, corner signal tracking is used to demonstrate that in the case of a concave tip wedge the corner signal is always merged with the Mach stem and never detaches. It is concluded that for the prediction of the Mach-to-regular reflection transition angle for wedges with concave tips, it is essential to predict as accurately as possible the strength of the Mach stem. An initial development of an analytical method to predict the transition angle is then provided.