Experimental study on the effectiveness of plasma energy deposition in controlling transverse jet

In this paper, we carried out an experimental study on the control of transverse jet via plasma energy deposition in a Mach 2.5 wind tunnel. The actuator operates at a discharge frequency of 10 kHz, generating thermal block effects upstream of the jet. Time-resolved schlieren system with 50 kHz shooting frequency, as well as wall static pressure taps, was utilized to measure the dynamic flow with and without excitation. This research delves into the feasibility of plasma energy deposition on controlling the transverse jets with varying injection total pressure (0, 200, 300, 400 kPa). The pressure increment within cavity resulting from discharge exists in all cases, attributed to the combined effects of plasma-induced shock and jet entrainment. Instantaneous schlieren images and the statistical analysis of their datasets were employed to investigate the unsteady characteristics of the flow field. The results indicate that discharge significantly elevates the energy contribution of unsteady modes, inhibits the low-frequency oscillations of the bow shock, and modulates the dominant frequency of the jet vortex shedding mode. Moreover, the increase in jet vorticity can be ascribed to the deformation of the precursor shock and the Richtmyer–Meshkov instability around thermal bubble/bow shock interaction region. As injection total pressure increases, the triangular-like region formed by the large eddy-induced shock, reflected shock, and the jet moves upstream and shrinks, consequently curtailing the region where jet pulsations amplify. After passing through bow shock, the effect of precursor shock on regulating the flow dampens with increasing injection total pressure. However, even at an injection total pressure of 400 kPa, coherent structures downstream of the bow shock can still be detected, demonstrating the broad control range of plasma energy deposition.