Experimental Study of Three Stream Coaxial Jets

Abstract

A core Mach 2 jet from the convergent-divergent nozzle in the presence of two coaxial sonic streams from convergent nozzles was investigated experimentally at different nozzle pressure ratios using visualization technique. The jet field was visualized using shadowgraph for nozzle pressure ratio (NPR) 3 to 6. From the visualization results, it was observed that the core length of Mach 2 jet for NPRs 3 to 6 increased with increasing coflow NPRs, indicating reduced mixing of coflow three stream jets as compared to Mach 2 jet (without coflows). From the present study, it was clear that the use of two sonic coflows on Mach 2 jet would result in core elongation for all the NPRs thus acting as a mixing inhibitor. But the sonic coflows were found to weaken the waves in Mach 2 jet, which is advantageous from the aeroacoustic point of view.