Effects of yaw on low angle injection into a supersonic flow

This paper presents the results of a study of transverse gas injection into supersonic/hypersonic streams with low downstream transverse angles in addition to yaw angles varying from zero to approximately 30 deg. The primary data are concentration measurements, with nanoshadowgraphs and oil flow visualization pictures also included. Two sets of experiments were performed. The first set studied the effects of yaw angle, specifically beta = 15 and 28 deg, on a helium injector with a 30-deg transverse angle in a Mach 3 freestream. Axial measurement stations were x/d = 30, 50, and 100. It was found that, as beta was increased, the maximum concentration mixing rate did not vary, but the jet core penetration decreased more at beta = 15 deg than at beta = 28 deg. A shearing effect between the portion of the jet in the boundary layer and the portion in the freestream increased the area of a typical constant concentration contour. The second set of experiments, conducted at NASA Langley, studied the effect of yawed injection at a transverse angle of 15 deg in a Mach 6 flow. Axial stations of x/d = 20, 40, 60, and 80 were used. A yaw angle of beta = 15 deg was found to decrease both the jet core mixing rate and penetration. The primary benefit of yaw was to increase lateral spreading. For similar injection conditions, the results show less near-field mixing at Mach 6 than Mach 3, but a faster mixing rate in the far-field at Mach 6.