Experimental Study on the Dynamic Characteristics and Surface Arc Plasma Control of Shock Train in the Supersonic Inlet

Abstract

The oscillation characteristics and morphological changes of the shock train in the inlet expansion section and the control of the shock train by surface arc plasma were studied in Mach 2 supersonic flow. A wedge installed at the exit of the supersonic inlet created a throttling ratio of 50% to generate a shock train in the expansion section. A high-speed schlieren system was employed to capture the flow structure of shock train. The fast Fourier transform (FFT) and snapshot proper orthogonal decomposition (SPOD) methods were employed to identify the oscillations’ spectral characteristics and for modal analysis of the shock train, respectively. The results show that the oscillation of λ leading shock has the characteristics of multipeak frequencies with a range of 300–500 Hz, and the Mach disk dominates the low-frequency oscillation characteristics of the λ leading shock. The surface arc plasma actuation has a significant control effect on the shock train, realizing the conversion of the λ leading shock to the oblique shock. As the first exploration of controlling the shock train in a supersonic inlet by surface arc plasma actuation, we found that the leading shock is transformed from λ shock to oblique shock because of the excitation. During the whole control process, although the actuation changes the shape of the leading shock, the position of the leading shock hardly changes. The blast wave and the control gas bubble induced by the surface arc plasma actuation possibly can weaken the oscillation of the shock train and make it relatively stable in a certain position. In practice, there is a risk that the shock train will be pushed out of the inlet due to the back pressure. Surface arc plasma actuation may be able to balance the back pressure and suppress the excessive advance of the shock train. In the future, we will verify this and further expand the control ability of surface arc plasma actuation on the shock train.