# Effect of NS-DBD Actuator Parameters on the Aerodynamic Performance of a Flap Lifting Device
## 5 Conclusions  
In this paper, the effects of three discharge parameters of the NS-DBD plasma actuator, i.e., the frequency, pulse width, and energy, on the flow field control of the flap lift device are studied and discussed. From the comparison and analysis of the aerodynamic change and flow field structure, the results show the following:  
(1) Comparisons of different discharge frequencies at three discharge positions. The increase of frequency has a position effect on the drag reduction at different positions, but the effect on the lift coefficient is different: The lift increment decreases at the lower trailing edge, the lift increment increases at the upper trailing edge, and the lift coefficient changes little at the upper surface. Therefore, the lift-drag ratio decreases when the frequency increases. It can be inferred that the increase of frequency cannot improve the excitation effect at the position where the original excitation effect is general, while it can enhance the original control effect at the position with obvious control effect. On the whole, the discharge frequency of 200 Hz is not better than 100 Hz, and the optimal discharge frequency needs to be further studied and analysed.  
Figure 21: The pressure distribution under single pulse discharges with different energy densities.  
Figure 20: The vorticity distribution under single pulse discharges with different energy densities.  
(2) The increase of discharge pulse width has a more significant effect on the flow field. A proper increase of pulse width can yield a better drag reduction effect and lift increase effect after stall, but when the pulse width is too large (500 ns), the control effect will be worse. After our comparison, it is found that the comprehensive excitation effect is better when the discharge pulse width is 100 and 200 ns, which are reference values for subsequent research.  
(3) While the increase of discharge energy enhances the perturbation of the pulse, it also contributes to some adverse effects. It does not optimize the control efficiency of lift increasement and drag reduction. When the discharge energy is too small, it is difficult to achieve the control effect because the disturbance decays too quickly. In addition, the increase of discharge energy is likely to lead to the high temperature of the flow field and the breakdown of the actuator, so in regard to the discharge energy, it is not true that larger is better. Therefore, further analysis is needed based on specific cases.  
Conceptualization: C.K. and Z.-W.S., Methodology: C.-Y.W., Data Curation: C.-Y.W., Formal Analysis: K.C. and C.-Y.W., Writing--Original Draft Preparation: K.C. and C.-Y.W., Writing--Review & Editing: K.C. and Z.-W.S.  
This work was supported by the National Defense Pre-Research Foundation of China (Grant No. KO21021), the Foundation of the National Key Laboratory of Transient Physics, and the Foundation of the Defense Technology Innovation Special Field.  
We are very grateful to [PERSON] and [PERSON] for their help in the research process and the financial support provided by the national defense pre-research foundation of China. Finally, I would like to thank the reviewers and editors for their suggestions and help in the process of revision.  
The authors declare no conflict of interest.