Rayleigh Scattering Measurements of Shock Enhanced Mixing

Abstract

This investigation was concerned with the nuxmg which occurs after the unsteady interaction of a shock wave with a laminar jet of helium. The jet of helium was injected normal to the direction of the propagation of the shock. The primary diagnostic, planar Rayleigh scattering, had sufficient spatial and temporal resolution to resolve the smallest diffusion scales present and allowed helium mole fractions to be measured in twodimensional planes normal to the original jet flow direction. The amount of molecular mixing was evaluated with a mass distribution function at increasing times after the shock interaction. The total masses of helium contained in regions where the molar concentration of helium was at least 30% and 50% were also calculated. The shock Mach number was varied, and the effect of a reflected shock was studied. It was found that shock interactions can significantly increase the mixing between the air and helium. A rough collapse of the mixing data occurs when time is normalized by the jet radius divided by the change in velocity of the air behind the shock. An increase in the enhancement of mixing occurred after the interaction with the reflected shock.

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