Mach reflection research - paradox and progress

The failure of the two-shock theory to adequately describe the conditions at which transition from regular to Mach reflection occurs, and of the three-shock theory to describe the Mach reflection of shocks with a strength less than about Mach 1.5 are described and discussed. The failures occur when the assumptions used in the theories are not fulfilled. It is suggested that the particle velocities behind the reflected and Mach stem shocks in the region of the triple point may, as a result of the curvature of these shocks, have transverse components. A revised three-shock solution is discussed, together with modifications of the Mach reflection phenomenon in truly unsteady configurations and for very strong incident shocks.