Density Variation due to Reflected Shock-Boundary-Layer Interaction

The interaction of the reflected shock with the incident shock boundary layer has been investigated using strip-film schlieren interferometry. The effect of boundary-layer separation was observed to disappear within 50 μsec after passage of the reflected shock; thus the late density behavior is governed solely by the flow properties ahead of the reflected shock and by the chemical properties of the gas. Marked reflected shock decelerations near the back wall were observed only when endothermic reactions occurred behind the reflected shock, with subsequent acceleration due to the increasing strength of boundary-layer separation and shock bifurcation. Reflected shock density varied according to [Δρ/ρ5(0)] = ktN (0.4 ≤ N ≤ 0.9), after boundary-layer-separation effects had disappeared and before the effect of transition occurring in the boundary layer ahead of the reflected shock was felt. Relative bifurcated foot velocities increased with increasing Mach number and decreasing specific heat ratio. The mechanism causing the growth of the foot is discussed.