This study focuses on mixing in a shear layer developed from helium slot injection into a parallel supersonic airstream and compares the results to those of previous slot-injection tests. In addition to short-duration schlieren and shadowgraph photography, concentration, pitot, cone-static, and stagnation temperature measurements are presented to document the development of the mixing layer. As anticipatet, slot injection shows poor initial penetration of the injectant into the freestream, and therefore poor initial mixing. Nevertheless, the helium case shows better mixing than a similar air-injection case of a previous experiment; the mixing layer grows 25 % larger than that in the air case by the last streamwise station. Also, about 30 % more freestream air is entrained into the shear layer in the helium case and is confined mainly to the top third of the mixing layer. The higher mixing rate stems from larger gradients in velocity and density and lower mass-flux ratio values that results in greater turbulent transport in the helium, injection test. Measurements of organized structure angles and intgral length scales are obtained using a parallel-array, dual-wire probe. Experimental results indicate the existence of organized structures in both the helium-injected and air-injected shear layers. The orientation of the measured angles is found to correlate with the local slope of the velocity profile. The integral length scale is on the order of 4 mm for both cases.
Experimental investigation of a supersonic shear layer with slot injection of helium
Experimentelle Untersuchung einer Überschallschersicherheit mit Schlitzeinspritzung von Helium
AIAA Journal ; 29 , 9 ; 1426-1435
1991
10 Seiten, 16 Bilder, 30 Quellen
Aufsatz (Zeitschrift)
Englisch