Corrugated Tabs for Enhanced Mixing of Supersonic Elliptic Jet

The present study quantifies the mixing efficiency of triangular tabs with and without corrugation, in the presence of favorable and adverse pressure gradients. Measurements were carried out to study the effects of square corrugations on triangular tabs in controlling the mixing of a supersonic elliptic jet of Mach number 1.5 of aspect ratio 3.37. The blockage caused by the simple tab is 2.5% each for two tabs. Whereas, for the corrugated tab, the corrugations over the tab side bring down the geometrical blockage to 2.2%. The experiments were carried out for nozzle pressure ratios (NPR) 3, 4, 5, 6, 7, and 8, covering both favorable and adverse pressure gradients. The pitot pressure variation along the axis (CPD) of the jets, without control, corrugated, and uncorrugated tabs, revealed that both tabs are leading to a considerable mixing enhancement of the supersonic elliptic jet at all pressure conditions studied. But, unlike the axisymmetric jet, the CPDs for both of the tabs overlap, especially in the near-field region. The core length for the uncontrolled jet is around five times the equivalent exit diameter of the nozzle exit (5D); whereas, it comes down to about one times the equivalent diameter of the nozzle exit (1D) for both the tabs at NPR 3. Therefore, both simple and corrugated triangular tabs at the minor axis could reduce the core length by about 80%. Therefore, the performance of corrugated triangular tabs to control the elliptic jet is similar to the simple triangular tabs. But, since the blockage offered by the corrugated tabs is smaller, it is advantageous from a propulsion point of view.