21st Congress of International Council of the Aeronautical Sciences, Melbourne, Australia, 13-18 September, 1998
Paper ICAS-98-3.5.2

MIXING DUE TO A SUPERSONIC MAIN STREAM AND CO-FLOWING SUPERSONIC PARALLEL JET

Tarnopolsky A. Z., Gai S. L.
University of New South Wales, Australia

Keywords: mixing, supersonic , parallel jet

The effect of configuration of nozzle shapes on the mixing layer formed by two supersonic streams is investigated in the present paper. A Mach 1.2 helium jet , simulating a fuel injector, was injected parallel into a Mach 2.0 main air stream. Three injectors were employed with a single slot, five slot and five circular nozzles. The injectors had been designed to provide the same helium mass flow in each case. Measurements included schlieren photography, two types of holographic interferometry and differential holographic interferometry. Supplemental laser-two-focus velocimetry and pressure fluctuation measurements were also carried out. An approximate method for the evaluation of mixing performance has been developed using results from schlieren flow visualisation and temporal average holographic interferometry. Qualitative information about the mixing process has also been obtained from differential interferometry. The comparison of different nozzle shapes have shown that contact area between jets and surrounding air is a significant factor affecting mixing efficiency. Flow visualisation techniques did not show the vortex structures in the mixing layer. However, differential interferometry has revealed that weak vortex like structures still persist especially behind the plain trailing edge injector.

view full paper