# Effect of NS-DBD Actuator Parameters on the Aerodynamic Performance of a Flap Lifting Device
## 4 Simulation Results and Analysis
### Comparisons of Discharge Frequency
#### 4.1.2 Comparative Analysis of the Flow Field Structure  
(1) Lower Trailing Edge Actuation  
Figure 7 shows the influence of the intensity of the plasma aerodynamic actuation with the change of discharge frequency at the lower trailing edge from the perspective of vorticity. The size of the shedding vortex is smaller, and the diffusion speed is slower at a 200 Hz frequency. Observing the vorticity distribution after the first pulse, it can be seen that the shedding vortex caused by the 100 Hz discharge frequency has slipped to the middle part of the separation area on the upper surface of the flap, while the vortex generated by the 200 Hz discharge frequency has just started to touch the area of large vorticity. As seen from the vorticity distribution after the 5 th, 10 th, and 20 th pulses, the vortices generated by the high-frequency discharge are more likely to accumulate on the upper surface of the flap, and the shedding speed is less than the low frequency (100 Hz), which causes the vortexes generated by each pulse excitation to fail to separate from each other, forming a large vorticity area that has a larger area. Therefore, the integration and reattachment effect of the flow in the separation zone is not as good as that of the 100 Hz discharge frequency, which is also reflected in the aerodynamic force.  
(2) Upper Trailing Edge Actuation  
Figure 8 shows that the shedding vortex generated by the high frequency discharge at the upper trailing edge is different from that at the lower trailing edge. Although the vortices are also small in  
Figure 6: The lift-drag ratio curve at different discharge frequencies.  
Figure 7: The vorticity distribution after the first, 5 th, 10 th, and 20 th pulses, stimulated by the different discharge frequencies at the lower trailing edge position.  
size, they slide alone and independently from the upper surface of the flap instead of joining together. Compared with the 100 Hz pulse excitation, the 200 Hz discharge frequency has better control ability of the separation flow on the upper surface of the flap: The shedding vortex is small in size and close to the wing surface, while the size of the vortex caused by the 100 Hz discharge frequency is too large to be closely attached to the upper surface of the flap, and it is easier for it to cause a flow with a large vortex on the surface in the propagation process. Thus, the increase of the frequency has a positive effect on the pulse excitation. In addition, the velocity distribution shows that the final separation region is smaller when the frequency increases.  
(3) Upper Surface Actuation  
The vorticity distribution caused by the upper surface pulse actuator when the discharge frequency changes is shown in Figure 9. The discharge at 200 Hz can cause more frequent vortex shedding. However, because the position of the pulse actuator has little influence on the flow area on the upper surface of the flap, the actual effect is not much different, even if there is a slight disturbance reflected in the vorticity distribution.  
Figure 8: The vorticity distribution after the first, 5 th, 10 th, and 20 th pulses, stimulated by the different discharge frequencies at the upper trailing edge position.  
Figure 9: The vorticity distribution after the first, 5 th, 10 th, and 20 th pulses, stimulated by the different discharge frequencies at the upper surface position.  
In addition, the influence of the discharge frequency on the effect of the pulse actuator is also verified under the condition of the 20\({}^{\circ}\) flap deflection, and the results show a similar law to that of the 10\({}^{\circ}\) flap deflection.