Diffraction of Strong Shock Waves by a Sharp Compressive Corner

摘要

The diffraction of strong shock waves in oxygen, in dissociation equilibrium, by a sharp compressive corner was investigated both theoretically and experimentally. The continuous curvature of the reflected shock wave R, for usual Mach reflection, changes when the pressure behind the bow shock generated by the wedge exceed that behind R. The appearance of a second triple shock system in irregular Mach reflection can be predicted from usual gasdynamic considerations without requirements from chemical kinetics. The location of the point where R kinks was also predicted. The above predictions are supported by the experimental results. The relative velocity between the first and second triple points can also be found, making it possible to do a useful analysis of conditions near the second triple point. Diffraction patterns for different gases (O2, N2, A and CO2) were investigated. An approximate solution was obtained from the first triple point trajectory angle as a function of incident shock Mach number and the wedge angle for dissociated oxygen. With the exception of small wedge angles and strong incident shocks, the agreement with experiment is good. Some reasons for the disagreement are given. An analysis was also made for oblique shock wave relations with imperfect gas effects (vibration and dissociation) including a two-shock confluence (regular reflection) and a three-shock confluence (Mach reflection). (Author)