Experimental Study of Mixing in a Turbulent Jet/Shock Interaction

Abstract

An experimental study on the interaction of weak shock waves with turbulent axisymmetric jets was conducted to explore mixing augmentation during such interactions. The experimental configuration is an axisymmetric nonhomogeneous jet that is processed by weak normal shock waves propagating along the jet axis. Experiments involved three combinations of jet gas and surrounding medium densities spanning density ratios 0.09 ≤ ρ _j / ρ _∞ ≤ 1.52. The oncoming shock strengths varied between Mach numbers 1.1 and 1.5. Planar laser-induced Rayleigh light scattering was utilized to obtain jet fluid concentration distributions. These images along with Schlieren photographs indicate that a strong interaction takes place around the jet downstream of the shock wave. In this region, the lateral spread of the jet increases as a result of strong baroclinic vorticity deposited along the jet boundaries. Quantitative analysis of the planar concentration images reveal that the spatial probability distributions of the jet fluid concentration are markedly different for jets with and without shock interaction. Jet fluid concentration levels are lower and more uniform in the regions processed by a shock wave. The degree of mixing enhancement appears to be weakly influenced by shock strength. The reversal of density ratio between jet and surroundings, and the consequent change in the sign of the baroclinic vorticity do not seem to influence the degree of mixing enhancement greatly.