Abstract
Mixing characteristics of a Mach 2 elliptic jet, with rectangular tabs placed along the major and minor axes are studied, at different levels of nozzle expansion. At all the pressure ratios, the jet with tabs along the minor axis experiences better mixing than the jet with tabs along the major axis. Also, at all the nozzle pressure ratios, the tabs along the major axis retard the mixing promotion, leading to core longer than the uncontrolled jet. For the range of nozzle pressure ratios studied, the mixing promotion caused by the tabs along the minor axis is the most effective for the highest studied overexpansion level corresponding to nozzle pressure ratio 4, leading to a core length reduction of 65%. The least mixing promoting efficiency for this orientation of tabs is found at the marginally underexpanded level of nozzle pressure ratio 8, at which the core length reduction caused is just 5%. The mixing promoting capability of the tabs along the minor axis is found to decrease with decrease in the adverse pressure gradient at the nozzle exit. The contour plots reveal that the tabs along the minor axis bifurcates the jet into two parts, causing faster spreading of the jet along the major axis than along the minor axis. As a result, there is no evidence of axis switching in the jet with tabs along the minor axis. The shadowgraph pictures show that the waves present in the core of the jet with tabs along the minor axis is weaker than the waves in the jet with tabs along the major axis and the uncontrolled jet. Also, the bifurcation of the jet with tabs along the minor axis is clearly captured in the shadowgraph images.
Published Version
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