Shifted Triangular Tabs for Supersonic Jet Control

This article presents the aerodynamic mixing efficiency of triangular and inverted triangular tabs, placed in a Mach 2 supersonic jet at $0D$, $0.25D$, $0.5D$, and $0.75D$ downstream of the nozzle exit, in the presence of different levels of nozzle expansion in the range from 0.383 to 1.022. Both tabs offer the same blockage of 5% of the nozzle exit area. The results show that the mixing caused by the triangular tab with its vertex down is better than an inverted triangular tab for all the tab positions tested in this study. Among the shifted locations, $0.5D$ proves to be the best location, resulting in a core length reduction of 68% for the triangular tab, in the presence of a marginal favorable pressure gradient of 2.2%, corresponding to nozzle pressure ratio 8. However, this mixing promotion is considerably lower than that by the same tab at the nozzle exit ($0D$) at the same nozzle pressure ratio, which promotes mixing, leading to a core length reduction up to 92%. But even at the $0D$ position, the core length reduction caused by an inverted triangular tab, at nozzle pressure ratio (NPR) 8, is only 35.6%.