Experimental study on enhancement of supersonic twin-jet mixing by vortex generators

Abstract

Experimental results on the mean flow evolution and the control of single and twin compressible jets at Mach 1.6 are presented. The jets issue from conical CD nozzles closely placed side-by-side resembling the twin nozzle configuration of supersonic aircrafts. The results are relevant to scenarios where turbulent jet mixing, supersonic core length, thermal radiation and acoustic loading are of concern. Experiments show that closely spaced twin jets grow, merge and interact near the inter-nozzle region that influences the characteristic decay and jet spread. Moreover, the deviation in centerline characteristic decay is more significant at off-design conditions. Vortex generators in the form of small metallic rectangular tabs mounted at the nozzle exit plane in different azimuthal orientations are used to control the mixing characteristics and the spread of these jets. Abrupt reduction in the core length and suppression of shock cell structure is achieved in over to under-expanded conditions. Furthermore, the orientation of vortex generators is found to significantly influence the development of jet flow field. The jet bifurcation and formation of daughter streams with distorted quasi-periodic shock cells structure are visualized using the schlieren technique. The underlying mechanisms for the observed effects and the behavior of daughter streams are discussed.