Plasma synthetic jet (PSJ) is widely employed in flow control due to its advantages of zero-mass and fast-response. A novel measurement method for high-frequency dynamic drag variation was adopted in a Mach 8 wind tunnel experiment, demonstrating that the opposing PSJ can achieve a maximum drag reduction of 40.27% and an average drag reduction of 13.25% within one discharge cycle. Subsequently, the numerical method was verified in detail and the effects of different discharge energies and nozzle diameters on the drag reduction characteristics of the opposing PSJ were studied. The results show that an increase in discharge energy is beneficial for the drag reduction characteristics of the opposing PSJ, although the efficiency remains relatively low. In contrast, increasing the nozzle diameter enhances the average drag reduction but significantly reduces the duration of effective control. The drag reduction mechanism of the opposing PSJ can be attributed to the combined effects of pushing the strong bow shock away to form a weaker oblique shock, followed by the reattachment of the shock downstream.

To effectively reduce shock wave loss at the trailing edge of a supersonic cascade under high back-pressure, a shock wave control method based on air jets is proposed. The air jet was arranged on the pressure side of the blade in the upstream of the trailing-edge shock. The flow control mechanism and effects of parameters were analyzed by computational methods. The results show that the air jet formed an oblique shock wave in the cascade passage which decelerated and pressurized the airflow. The resulting expansion wave downstream of the jet slot weakened the strength of the trailing-edge shock. This could effectively change the normal shock into oblique shock and thus weaken the shock loss. Optimal control effect was achieved when the mass flow rate ratio of the jet to the passage airflow remained 0.35–1.11% and the distance from the jet slot to the shock foot of the trailing-edge shock was about five times the thickness of the boundary layer. The proposed method can reduce the total pressure loss of a supersonic cascade, with the maximum improvement effect reaching 7.29% compared to the no-control state.