## 3 Experimental Results and Discussions
### PIV Measurement Results
The vortex concentrations of the case \(J_{sj}=0.0094\) are dramatically decreased and narrowed laterally and stretched in the flow direction, as shown in the right of Figure 10. This phenomenon of the POD modes is in connection with the elongation of the wake vortex, as shown in Figure 8b. In addition, the wake jet flow disturbs the vorticity. It divides it into two small parts at the nearing wake position as shown in modes one to four, and mode five changes to much smaller vorticity concentrating parts compared with case \(J_{sj}=0\). Based on the analysis above, the wake flow structure characteristics of the case \(J_{sj}=0.0094\) yield the unsteady aerodynamic force that is less than that of case \(J_{sj}=0\), which is consistent with the results in Section 3.2. To analyze the difference of the velocity profile in the flow field behind the test model with and without the trailing edge jets, the means of the streamwise velocity, streamwise velocity fluctuation, and the transverse velocity were extracted from the PIV measurement plane I. The time-averaged streamwise velocity that was located in different positions of X/B is given in Figure 11a. The velocity profile of the case \(J_{sj}=0\) is asymmetrical in the location that is close to the SBG model and symmetrical in a further downstream position. The reason is that the geometric shape of the SBG model is asymmetrical along the line of Y/B = 0. The lowest velocity of the case \(J_{sj}=0\) was less than that of the case \(J_{sj}=0.0094\) at X/B = 0.03 and 0.12 because the jet flow can alleviate the velocity defect. That indicates the inner region flow field behind case \(J_{sj}=0.0094\) is more stable than the case \(J_{sj}=0\)[6]. Conversely, the smallest value of the velocity of the case \(J_{sj}=0\) was larger than that of case where \(J_{sj}=0.0094\) at X/B = 0.21 and 0.30. The velocity profile of the case \(J_{sj}=0\) regained faster than that of the case \(J_{sj}=0.0094\). Moreover, the width of the wake flow in case \(J_{sj}=0\) was slightly wider than the case \(J_{sj}=0.0094\), indicating the large drag force that was acting on the SBG model without control [20]. Figure 10: The POD mode of the wake flow in measurement plane I. (**a**) mode 1, (**b**) mode 2, (**c**) mode 3, (**d**) mode 4, and (**e**) mode 5. Figure 11b shows the fluctuation of the streamwise velocity profile at various positions in the wake. For the case \(J_{ji}=0\), There are two peak values that were observed in the wake flow of the case at X/B = 0.03-0.30, i.e., double-cusp mode. The maximum values appear when the turbulence level grows a dramatically quick ratio, mainly in the shear layers of the separation flow [33]. However, owing to the trailing edge jet flow disturbing the original flow field a the near-wake of X/B = 0.03, this profile for the controlled case exhibited a quadruple cusp mode. The fluctuation of the streamwise velocity profile of the case \(J_{ji}=0.0094\) presented a double-cusp mode at X/B = 0.12-0.30. It was similar to that of the case \(J_{ji}=0\), illustrating that the jet flow has a short influence range, which is identical to the investigation by [PERSON] et al. [20]. Moreover, the peak value of the streamwise velocity fluctuation for case \(J_{ji}=0.0094\) was lower than the case \(J_{ji}=0\) at all the positions, leading to the unsteady drag force that was being exerted in the SBG model being mitigated. The profiles of the transverse velocity fluctuation for cases \(J_{ji}=0\) and \(J_{ji}=0.0094\) are plotted in Figure 11c. The maximum value appears at approximately Y/B = 0.02, which is the axis of symmetry for the wake flow. The shear layers that are formed from the upper and lower surface are amalgamated and violently interact, causing a significant transverse velocity fluctuation [18; 20].