Fig. 1. Flow field of airfoil dynamic stall within a pitch period.^[13]

Fig. 2. Airfoil installation and experimental layout in wind tunnel.

Fig. 3. Airfoil oscillation drive device.

Fig. 4. Deployment of actuator at the leading edge of airfoil and electrical parameter measurement: (a) deployment of actuator. (b) system of electrical parameter measurement.

Fig. 5. Characteristics of NS-DBD in still air: (a) voltage and current curves of NS-DBD (V_{p – p} = 13 kV), (b) discharge image of NS-DBD, and (c) shock wave induced by NS-DBD experimental results.

Fig. 6. Static experimental lift coefficient C_L under different airfoil’s profile states.

Fig. 7. Baseline for various reduced frequencies of light dynamic stall.

Fig. 8. Flow control effects under light stall state (k = 0.05).

Fig. 9. Flow control effects under light stall state (k = 0.1).

Fig. 10. Flow control effects under light stall state (k = 0.15).

Fig. 11. Baseline for various reduced frequencies of deep dynamic stall.

Fig. 12. Flow control effects under deep stall state (k = 0.05).

Fig. 13. Flow control effects under deep stall state (k = 0.1).

Fig. 14. Flow control effects under deep stall state (k = 0.15).

Fig. 15. Flow field over a static airfoil with and without NS-DBD:^[30] (a) plasma off and (b) plasma on.

Fig. 16. Flow field with and without actuation for dynamic stall: (a) base flow field at high α, (b) flow field with actuation at high α, (c) flow field with actuation when airfoil pitching down to a certain degree.

Fig. 17. Analysis for effect of various k at certain α on downstroke: (a) k = 0.05 pitch-down motion, (b) k = 0.1 pitch-down motion, and (c) k = 0.15 pitch-down motion.