Jet mixing manipulation with asymmetric orientation of tabs

The jet mixing caused by two rectangular and triangular tabs of geometric blockage 2.5% each, separated by 90^⁰ at the nozzle exit plane of a Mach 2 circular jet, in the presence of varying levels of expansion, corresponding to nozzle pressure ratio (NPR) 4–8, was investigated experimentally. The relative mixing promoting capability of these tabs was assessed. It is found that the rectangular tabs at 90^⁰ interval retards mixing for NPRs 4, 5, and 6, and promotes mixing at NPRs 7 and 8. Comparison of the present result for rectangular tabs at 90^⁰ interval with that of Arun Kumar and Rathakrishnan ⁸ for 180^⁰ interval shows that the mixing promoting capability of 90^⁰ and 180^⁰ intervals are comparable, at NPR 7. But at NPR 8, the mixing performance of rectangular tabs at 90^⁰ interval is better than 180^⁰ interval. For NPRs 7 and 8, the core length reduction due to rectangular tabs at 90^⁰ and 180^⁰ are 26% and 36%, and 28% and 26%, respectively. On the contrary, the triangular tabs at 90^⁰ interval promote mixing at all NPRs of the present study. The mixing caused by triangular tabs at 180^⁰ interval reported in literature ⁸ is only marginally better than triangular tabs at 90^⁰ interval studied in this work. For NPR 4, 5, 6, 7, and 8, the core length reduction caused by triangular tabs, at 90^⁰ and 180^⁰ intervals, are 24%, 58%, 69%, 80%, and 76%; and 38%, 65%, 77%, 87%, and 85%, respectively.