Analysis of intermittency and probe data in a supersonic flow with injection

Abstract

Probe measurements were performed in the flow field produced by injection of helium or air into a supersonic airstream. The injectant was seeded with water and Rayleigh scattering was used to image the injectant plume. The region of the flow containing injectant–air mixture is seen to be highly unsteady, leading to the intermittent presence of injectant in certain regions. The intermittency is inferred. It is shown that bias errors can occur when the probe data is analyzed by techniques which assume steady flow. A technique for relatively bias-free analysis utilizing the intermittency measurements is presented and the bias errors are estimated. The gas-sampling probe is shown to measure the mass-weighted-mean mass fraction of helium, which is significantly less than the simple mean. A new measure of mixing efficiency obtained from the combined probe and intermittency measurements is discussed.