Flow field and acoustic characteristics of elliptical throat CD nozzle

The mixing characteristic of circular jet with elliptical throat is studied at different levels of expansion of the nozzle. Two kinds of configurations are studied in this paper, elliptical throat and circular throat jet. At all pressure ratios, the jet with non-circular throat experiences superior mixing than circular throat. The core length of elliptical throat jet is shorter than circular jet. Also, at all pressure ratios, the profile of both configurations looks identical in oscillation; however, the efficiency of the mixing promotion is high in non-circular throat. The promotion of mixing is most efficient at nozzle pressure ratio (NPR) level of 8. As the NPR increases, the core length of the jet reduces nearly 5–10% at each range of NPR. The centreline Pitot pressure profile of non-circular and circular throat shows that the decay of the jet from elliptical throat nozzle is faster than the jet from circular jet. At different levels of expansion, the shock structure shows notable changes with elliptical shape. The amplitude of screech frequency of the jet noise decreases with an increase in NPR. Introduction of elliptical throat to circular throat modifies the shock-cell structures, which significantly change the screech amplitude due to weakening of waves.