## 3 Results and Discussion
### Influence on Flow Mechanism of Integrated LPT-GV
In the upper area (h/H = 0.55-1.0), \(\rm Cp_{0}\) is almost consistent when \(f>0.90\), while it decreases significantly in the lower \(f\) cases. This is because the enhanced passage vortices near the shroud (PV1 in Figure 9) increase the total pressure loss in the corresponding region for the low \(f\) cases (i.e., \(f\) = 0.71). As the region of h/H = 0.36-0.55 is dominated by the detached passage vortex (PV2 in Figure 9), the strongest PV2 in the case of \(f\) = 1.61 causes the \(\rm Cp_{0}\) of the corresponding area to be the lowest among the three cases. In the lower region (h/H = 0-0.36), \(\rm Cp_{0}\) in the case of \(f\) = 0.90 is smaller than that in the other two cases. Since this region is dominated by the PV3 (as shown in Figure 9) and the separated flow on the middle section of LPT-GV, the previous conclusion indicates that the intensity of PV3 is almost the same in all cases, so the change of the loss in this region is primarily  
Figure 9: The \(\rm Cp_{0}\) contour of Sections C1-C5 and the limiting streamline on the LPT\(-\)GVs’ suction surfaces. affected by the flow separation. Compared with the case of \(f=0.90\), although the separation bubble size is larger in the case of \(f=0.71\), its duration is reduced, resulting in the decreased loss; in contrast, the separation bubble duration increases in the case of \(f=1.61\), but the sharp reduction of the separation bubble size also reduces the loss. In general, the most important influencing factor of sweeping wake on the LPT-GV loss is the passage vortices (PV1 and PV2) in the upper region, and both the thicker boundary layer on the shroud in the low \(f\) cases and the residual wake vortices around the casing in the high \(f\) cases can enhance PV1 and PV2, which means that there must be a suitable reduced frequency that can well suppress PV1 and PV2 to minimize the total loss of the LPT-GV. Figure 11 compares the loss (\(\Upsilon\)) of the integrated AITD and its parts for the various \(f\) cases. The loss of the AITD, including the wake dissipation and the end-wall boundary layer loss, first decreases and then increases with increasing \(f\), and its minimum value appears in the case of \(f=1.34\). This is because (1) when \(f<1.34\), the increasing distance between adjacent wakes weakens the wake interaction with increasing \(f\), which is conducive to reducing the mixing loss of wakes; (2) when \(f>1.34\), the enhanced mixing of wake vortices near the hub is more significant, and causes a substantial increase in the loss of wake mixing. The loss of LPT-GV, including passage vortices loss, separation bubble loss, boundary layer viscosity loss, and wake dissipation, is almost the same in all cases, which means that the loss is less affected by the sweeping frequency of the upstream wake as it is almost dissipated before entering the LPT-GV due to the long propagation path. However, it still decreases first and then increases with increasing \(f\), and its minimum value appears in the case of \(f=0.90\). This means that the sweeping wake can suppress the passage vortices in the top area of the LPT-GV channel well in this case, and \(f=0.90\) is the optimal reduced frequency to reduce the LPT-GV loss within the scope of this paper. Along with increasing \(f\), the total loss first decreases and then increases in the integrated AITD and reaches its minimum value in the case of \(f=1.34\), which is 2.67% lower than that in the case with the maximum loss (\(f=1.61\)). In comparison, the LPT-GV loss accounts for more than 80 of the integrated AID's total loss, and is the largest loss source. Figure 10: Pitchwise-averaged Cp\({}_{0}\) in Section B9.