Performance of Corrugated Limiting Tab in Presence of Sharp Corners

Abstract

The mixing promoting efficiency of a corrugated limiting tab placed at the exit of a Mach 1.86 square jet has been investigated experimentally. Mixing performance of tab having semicircular corrugations, at both the edges along its length and having 5% blockage, is compared with an identical tab of the same blockage without corrugations, at different levels of adverse pressure gradients beginning from 36.5% (NPR 4) to about 4.75% (NPR 6). It is found that, as high as 98.98% reduction of core length can be achieved with the semicircular corrugated tab, at NPR 5. This is considerably higher than the core length reduction of 68.31%, caused by the uncorrugated tab at NPR 5. Also, the mixing performance of semicircular corrugated tab is found to be independent of the level of overexpansion at the nozzle exit. The profile plots for the semicircular corrugated tab shows improvement in the jet symmetry in the direction along the tab and large jet spread is caused in the direction normal to the tab. The shadowgraph pictures for the uncontrolled and controlled jets clearly demonstrate the effectiveness of corrugated tabs in weakening the waves in the jet core
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