Numerical investigation of flow field inner cavity of high-temperature Plasma Synthetic Jet actuator

Abstract

A Plasma Synthetic Jet (PSJ) actuator is the promised equipment to produce a high-speed synthetic jet, which can be potentially applied to control the supersonic flow. Several researchers paid much attention to its application on Active Flow Control (AFC) in supersonic conditions, but the understanding of the flow field inner the cavity is extremely inadequate. This study aims to use experimental measurement and numerical simulation to reveal the variation of flow field during the issuing PSJ. The PSJ actuator driven by the capacitor group has been designed, and Large Eddy Simulation(LES) was conducted and verified by experimental data with high-resolution particle image velocimetry (PIV) and hot wire anemometer (HWA). The kinetic energy of the PSJ dominantly results from its thermal energy during the stage of plasma deposition, which makes the pressure and temperature of tiny volume near the electrode, increase sharply in microseconds. The electric discharge of the PSJ actuator is simulated by employing the energy input into the source term of the energy equation. The efficiency of the actuator was 20% is demonstrated in this study, which is consistent with the previous research. It is found that the high-pressure zone generated by plasma deposition shifts in a reciprocating way between the bottom and top of the cavity. The pressure inner the cavity and velocity of the PSJ attenuate while oscillating with the real-time. The geometry of the actuator paly a significant role in the performance of the PSJ. Keeping the cavity height constant, the frequency of the pressure is almost the same because the attenuating frequency is related to the cavity height. Increasing cavity height decreases attenuating frequency. The attenuation rate increases with the increase of orifice diameter and decreases of orifice height because of the leaking of gas from the cavity. The mathematic model is built and verified to describe the variation of pressure inner the cavity and the velocity of the PSJ.