We carried out an experimental study of Mach 2.5 airflow over a semicircular column with 15 kHz arc plasma energy deposition (APED). The APED was pulsed at microsecond time scales, and it rapidly added high-repetition-frequency thermal bubbles that propagated downstream. Time-resolved schlieren imaging with a frame rate of 30 kHz was utilized to record the dynamic flow fields. This study was aimed at investigating the effects of these thermal bubbles on the unsteadiness characterization of a shock wave/turbulent boundary layer interaction (STBLI) by some statistical methods based on the spatial gray value extracted from a sequence of time-resolved schlieren images. The results showed that APED pulsed at 15 kHz was highly effective in weakening both the separation shock and the attached shock continuously and in narrowing the low frequency component of the oscillatory separation shock. A stronger oscillation of the attached shock under APED was found. The thermal bubbles increased the characteristic scales of vortex in the incoming turbulent boundary layer and shear layer, enhancing the fluctuation of the shear layer with large numbers of high-frequency components. The continuous transforming of the enlarged eddies along the shear layer was regarded as the main cause of shock weakening and frequency modulation of the STBLI in this study.
Experiments and numerical simulations of shock wave/turbulent boundary layer interaction (STBLI) disturbed by arc plasma energy deposition (APED) were carried out in this paper. The experiments were conducted in a M = 2.497 wind tunnel. Both the flow structures and the evolution process of impinging STBLI disturbed by APED were captured by time-resolved schlieren imaging. The disturbance effects of APED on supersonic flow without STBLI were studied with different capacitor stored energies. Furthermore, under the same capacitor stored energy, the impinging STBLI control with APED were explored in different flow deflection angles. The experimental results indicated that thermal bubbles induced by APED had a high penetration depth and impacted the STBLI seriously. Compared to the incident shock wave, the separation shock wave was more sensitive to the influence of APED and showed significant instability. With equivalent energy deposited into the flow, the ability of APED to disturb the impinging STBLI was decreased as the flow deflection angle increased, and the separation shock wave had a smaller position change and shorter recovery time. The direct numerical simulation results showed that the APED added in a flow field can hinder the velocity development of the turbulent boundary layer. The unsteadiness of separation shock waves was induced by both thermal bubbles and blast waves, and the thermal bubbles' effects were dominant. They would modify the compressibility of the boundary layer and enlarge the separation zone, which contributed to the separation shock wave's dispersion and movement.
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