## 3 Results and Discussion
### Analysis of Surface Pressure Distributions  
Figure 7 shows comparisons of the distributions of the mean and fluctuating pressure coefficients around the test models with and without control at a negative wind attack angle of \(-20^{\circ}\). As shown in Figure 7a, the mean pressure coefficients on the upper surface of Case 0 and Case 4 are close to each other. Furthermore, the pressure gradients are positive and the flow will not separate from the upper surface. For Case 0, the fluctuating pressure coefficients are smaller on the windward side on the upper surface, as shown in Figure 7b. In the region near the trailing edge of the upper surface, the fluctuating pressure coefficients were relatively larger, which may be induced by the interaction between the alternating wake flows from the upper and lower surfaces. The fluctuating pressure coefficients on the upper surface of the test model in control Case 4 were slightly lower compared to Case 0.  
At the negative attack angle of \(-20^{\circ}\), the flow separation is mainly located on the lower surface. On the windward side of the lower surface, the adverse pressure gradient region of the Case 4 is wider than the Case 0 (Figure 7c), resulting in decreased fluctuating pressure coefficients in this region compared to the Case 0 results (Figure 7d). However, on the leeward side of the lower surface, the pressure gradients of Case 4 are decreased and the fluctuating pressure coefficients obtain a great reduction in comparison with Case 0 (Figure 7c,d). Combining the fluctuating pressure coefficients on the whole lower surface, the total aerodynamic force coefficients (i.e., the lift, drag, and moment coefficients) should be greatly reduced in the Case 4, which has also been validated by the results in Figure 6.  
Figure 7: Distributions of mean and RMS (root-mean-square) values of pressure coefficients at the wind attack angle of \(-20^{\circ}\): (**a,b**) are the upper surface and (**c,d**) are the lower surface.  
Figure 8 presents the comparisons of the distributions of the mean and fluctuating pressure coefficients around the test models with and without control at a positive wind attack angle of 15\({}^{\circ}\). At this angle, the flow separation is mainly located on the upper surface. On the leeward side of the upper surface, there is a large decrease in mean pressure coefficients and the adverse pressure gradient obtains an obvious reduction (Figure 8a). Following this, there is a dramatic decrease in fluctuating pressure coefficients of Case 4 compared to Case 0 results, as shown in Figure 8d.  
The results shown in Figure 8c,d are similar to those in Figure 7a,b. The mean pressure coefficient distributions of Case 0 and Case 4 are close to each other. The fluctuating pressure coefficients are slightly smaller than the results of Case 0, as shown in Figure 8c,d.  
Combining the results in Figures 7 and 8, it was found that the control Case 4 has less influence on the surface without a flow separation and greater effects on the surface with a flow separation. The control Case 4 can greatly decrease the adverse pressure gradient and fluctuating pressure coefficients. The reason mainly includes two aspects: first, the main flow on the surface without a flow separation will have the same movement direction as the jet flow. Therefore, the jet flow will hardly prevent or influence the main flow. Secondly, it is important to consider the main flow on the surface with a flow separation. In particular, the main flow has a reverse direction with the jet flow in the separation region. Thus, the interaction between the jet flow with the main flow will greatly influence the pressure distributions.  
Figure 8: _Cont._