Effect of tab length on supersonic jet mixing (original) (raw)

An experimental investigation has been carried out to assess the efficiency of rectangular tabs of 5% blockage with three different aspect ratios of 1, 1.5, and 2, in promoting the mixing of a Mach 1.73 axisymmetric free jet, in the presence of adverse and favorable pressure gradient, by varying the operating nozzle pressure ratio (NPR) from 4 to 8, in steps of 1, covering all the three levels of expansion, namely, the over-, correct-, and underexpaned states at the nozzle exit. For NPR 4, the Mach 1.73 jet is overexpanded with an adverse pressure gradient of about 23%. At NPR 5, the nozzle is almost correctly expanded with an adverse pressure gradient of only about 3%. At NPRs 6, 7, and 8, the nozzle is underexpanded with favorable pressure gradients of 16%, 35%, and 55%, respectively. It is found that as high as about 88% reduction in the core length is achieved by the tab with an aspect ratio of 1.5 at NPR 7. However, the reduction caused by tabs with aspect ratios of 1 and 2 is ...