Fig. 1. Working process of PADPA: (a) High voltage applied; (b) gas breakdown; (c) CGB generation.

Fig. 2. Plate size drawing

Fig. 3. PADPA working diagram

Fig. 4. NPLS system diagram

Fig. 5. Schematic diagram of high-speed schlieren system

Fig. 6. Nanosecond pulse power supply

Fig. 7. Discharge characteristic: (a) Voltage current waveform; (b) power waveform.

Fig. 8. Process of monopulse arc discharge: (a) The shape of arc; (b) the evolution of the excitation area.

Fig. 9. Schlieren display at different excitation frequencies: (a) f = 5 kHz; (b) f = 10 kHz; (c) f = 20 kHz.

Fig. 10. Velocity curve of precursor shock wave with time.

Fig. 11. Evolution of flow field characteristics of the exciter under incoming flow conditions: (a) f = 10 kHz; (b) f = 20 kHz.

Fig. 12. Basic flow field diagram.

Fig. 13. Flow field diagram when excitation frequency is 5 kHz.

Fig. 14. Flow field diagram when excitation frequency is 10 kHz.

Fig. 15. Flow field diagram when excitation frequency is 20 kHz.

Fig. 16. Flow field diagram when excitation frequency is 40 kHz.

Fig. 17. Flow field diagram when excitation frequency is 60 kHz.

Fig. 18. Transition parameters vary with excitation frequency: (a) Transition position varies with the excitation frequency; (b) length of transition zone varies with the excitation frequency.

Fig. 19. Five ways for boundary layer transition to turbulence.