Corrugated right-angled triangular tabs for supersonic jet control

Abstract

This paper compares the mixing promoting efficiency of two identical sharp and truncated vertex right-angled triangular tabs provided with semicircular, triangular, and square corrugations along its edges, offering geometrical blockage of 2.5% each, placed at the exit of a Mach 2 circular nozzle was studied experimentally. To quantify the effectiveness of the controlled jets in mixing, Pitot pressure along the jet axis and the jet spread along and normal to the tabs were measured, covering highly overexpanded and marginal underexpanded levels at the nozzle exit. The results reveal that the corrugated tabs enhance mixing higher than the uncorrugated (plain) tabs, for both sharp and truncated vertices. For the jet controlled with sharp vertex right-angled triangular tabs, a maximum reduction of about 91% in core length is caused by the square corrugation at NPR7. The corresponding core length reduction caused by semicircle, triangular corrugated, and plain tabs is about 87, 85, and 65%, respectively. For the jet controlled with truncated vertex right-angled triangular tabs also, the core length reductions are of the same order as those for the sharp vertex triangular tabs. The jet mixing is strongly influenced by the combined effect of tab geometry, corrugation shape, tip effect, and expansion ratio. The shadowgraph pictures clearly show that the waves in the controlled jets are made weaker than those of the uncontrolled jet.