Influence of volume and frequency parameters on opposing plasma synthetic jet for drag reduction in supersonic flow

Abstract

Shock wave drag reduction is of great significance to improve the performance and range of supersonic/hypersonic vehicles. As a new active flow control method, plasma synthetic jet actuator (PSJA) shows great potential in the field of shock wave drag reduction. The influence of volume and frequency parameters on opposing plasma synthetic jet (PSJ) for shock wave drag reduction of a hemisphere in M = 3 flow is investigated using numerical method. The first part of this study focuses on the effects of PSJA cavity volume and hemisphere volume on the drag reduction characteristics of opposing PSJ. As the input energy is constant, the average drag reduction increases with the increase of PSJA cavity volume but decreases with the increase of hemisphere volume. In addition, it is found that the trend of the average drag reduction as a function of the volume ratio (the ratio of PSJA cavity volume and hemisphere volume) fits a logarithmic law. Next, the drag reduction characteristics of high frequency opposing PSJ, and the effect of discharge frequency are investigated. There is a “self-balancing process” when opposing PSJA operates at high frequency. The physical meaning of the “self-balancing process” is that the PSJA automatically prolongs the suction recovery time and shortens the jet ejection time in order to maintain continuous operation. After the “self-balancing process”, the PSJA eventually maintains a pseudo-steady operating state. The dimensionless frequency (the ratio of discharge frequency and Helmholtz resonance frequency) is an important parameter that affects opposing PSJ. The average drag reduction is basically equal when the dimensionless frequency is less than 1, about 11%, but decreases significantly when the dimensionless frequency is about 1, about 8%. The effects of volume and frequency parameters on the flow field characteristics of opposing PSJ are also analyzed.