## 3 Experimental Results and Discussions  
### Surface Pressure Distribution  
The pressure coefficient (C\({}_{pi}(t)\)) was that the surface pressure results that were acquired by the pressure measurement experiment were nondimensionalized by the dynamic pressure and defined as Equation (2). The mean value of the external surface pressure coefficient (C\({}_{p}\_M\)) was defined as Equation (3) to illustrate its average features. We used the standard deviation of the external surface pressure coefficient (C\({}_{p}\_R\)) to describe the fluctuating characters of the pressure distribution, as given in Equation (4). \[C_{pi}(t)=\frac{2(p_{i}-p_{\infty})}{\rho{\rm{I}}{\rm{O}}_{0}^{2}} \tag{2}\]  
\[C_{p}\_M=\frac{1}{N}{\sum\limits_{i=1}^{N}{C_{pi}(t)}} \tag{3}\]  
\[C_{p}\_R=\sqrt{\frac{1}{N}{\sum\limits_{i=1}^{N}{\left({C_{pi}(t)-\overline{C_{pi }(t)}}\right)}^{2}}} \tag{4}\]  
where \(p_{i}\) is the static pressure that is acting on the surface SBG model and \(p_{\infty}\) is the static pressure of the free stream. The time histories of \(p_{i}\) and \(p_{\infty}\) are acquired and recorded by the digital pressure scanner. \(\rho\) is the air density and \(N\) is the length of the total sample. It should be illustrated that the surface pressure measurement plane was located in the central cross-section (i.e., plane II as given in Figure 1a) was far away from the jet holes. The pressure distribution on other cross-sections may be different. However, the aerodynamic force that was acting on the present cross-section of the controlled case might underestimate the control ability due to the pressure measurement section being the farthest distance from the cross-section with trailing jet hole [26]. The PIV result will confirm that. Figure 4 gives the external surface pressure coefficient that was distributed around the SBG model that was equipped with and without trailing edge jets. For the case \(J_{ji}=0\), the mean pressure result of the upper surface on the SBG model shows a dramatic decrease due to an inflection point that existed between the pressure measurement taps 1 and 2. The adverse pressure gradient was observed at the range of X/B from 0.11 to 0.20, as shown in Figure 4a. Therefore, the flow separation occurs in that position, causing the fluctuating pressure to have a maximal value at X/B = 0.11, as shown in Figure 4c. As the X/B was larger than 0.20, the mean pressure distribution of the upper surface had similar values, except for the position of X/B = 0.5 and near the trailing edge. The upper external surface pressure distribution fluctuation shows an enormous value when X/B gets close to 1. The reason for this is that the position nearing the trailing edge will be more influenced by the alternating vortex shedding [20,26]. The adverse  
Figure 3: Sketch of the PIV experiment arrangement. pressure gradient also appears in the lower surface of the SBG model at the position of X/B = 0.31-0.41 as shown in Figure 4b, and the peak value of the fluctuating pressure coefficient was obtained at the position of X/B = 0.31, as given in Figure 4d. Therefore, the local flow separation also occurred at the corner point between the pressure measurement taps 29 and 30. The other characteristics of the lower surface pressure are similar to those of the upper surface pressure. When the jet holes were inserted in the SBG model, the external surface pressure was modified compared to that of the case \(J_{sj}=0\). The mean values of the external surface pressure of the controlled case with different non-dimensional jet momentum coefficients remain close to the uncontrolled case at the position nearing the leading edge of the SBG model. When the pressure taps were located at the trailing edge, the mean value of the external surface pressure was alleviated by the trailing edge jet flow, and the case \(J_{sj}=0.0094\) exhibited the best control effect. All the controlled cases can slightly attenuate the local flow separation at X/B = 0.11 of the upper surface of the SBG model, as shown in Figure 4c, compared to case \(J_{sj}=0\).