Experimental study on surface arc plasma actuation-based hypersonic boundary layer transition flow control

Effective control of hypersonic transition is essential.In order to avoid affecting the structural proflle of the aircraft,as well as reducing power consumption and electromagnetic interference,a low-frequency surface arc plasma disturbance experiment to promote hypersonic transition was carried out in theΦ0.25 m double-throat Ludwieg tube wind tunnel at Huazhong University of Science and Technology.Contacting printed circuit board sensors and non-contact focused laser differential interferometry testing technology were used in combination.Experimental results showed that the low-frequency surface arc plasma actuation had obvious stimulation effects on the second-mode unstable wave and could promote boundary layer transition by changing the spectral characteristics of the second-mode unstable wave.At the same time,the plasma actuation could promote energy exchange between the second-mode unstable wave and other unstable waves.Finally,the corresponding control mechanism is discussed.

Suppressing unsteady motion of shock wave by high-frequency plasma synthetic jet

Three Plasma Synthetic Jet Actuators(PSJA)under the high-frequency actuation are used to control the Shock Wave Boundary Layer Interaction(SWBLI),a high-speed schlieren image processing method based on spatial Fourier transform as well as snapshot proper orthogonal decomposition were used to study the control effect of high-frequency plasma synthetic jet on lowfrequency unsteadiness of SWBLI.The analysis of the base flow shows that the separated shock wave actually has both large-and small-amplitude vibrations at low frequency.And the results revealed that the PSJA with an operating frequency of 2 k Hz has the ability to reduce the energy of low-frequency component of shock wave motion,indicating that the 2 k Hz actuation can effectively suppress low-frequency unsteadiness of the separated wave.Compared with the actuation frequency of 2 k Hz,the energy of low-frequency component of the shock wave is enhanced under the8 k Hz actuation,which aggravates the low-frequency unsteady motion of the shock wave.It is likely that the actuation frequency is too high,thus the intensity of the precursor shock wave induced by PSJA becomes weaker.Additionally,as the 4 k Hz actuation is applied,the pulsation of the separation region was enhanced,it is speculated that the actuation frequency is coupled with the oscillation frequency of the separation region.