Study on the combined effect of various injection conditions on the drag reduction by a counter-flow jet in supersonic flow

Abstract

Parametric investigations of drag reduction by counter-flow jet in supersonic flow have been conducted through numerical simulations. An axisymmetric RANS equation was solved to analyze the drag reduction effect of each parameter. This study revealed a general tendency of the drag reduction effect on various shapes and counter-flow jet conditions and confirmed the conditions for obtaining the maximum drag reduction. In addition, the counter-flow jet structure and flow transition were also analyzed. Five parameters, jet mass flow rate, nozzle size, nozzle exit Mach number, gas total temperature, and gas types, were applied to analyze the drag reduction and flow structure. The results showed that the jet mass flow rate is the dominant factor of drag reduction and flow transition by counter-flow jet and the nozzle size has little effect on drag reduction. Regarding the individual effects of each parameter, a high nozzle exit Mach number, high total temperature, and low molecular weight of the gas are desirable for a higher drag reduction ratio with a low mass flow rate. On the other hand, because a thrust reversal phenomenon tends to occur easily at high temperatures, proper trade-off between each parameter is essential for obtaining the maximum drag reduction ratio. In addition, the nozzle flow conditions, particularly the static pressure ratio at the nozzle exit, have a large effect on the flow structure of the counter-flow jet.