## 4 Conclusions  
A dynamic simulation was launched to study the influence of HPT rotor wake passing frequency on the flow mechanism in an integrated AITD. Sweeping rods were adopted to replace the HPT rotors to isolate the effect of its wake from those of other secondary flows. Along with increasing reduced frequency, the circumferential motion of the wake was also accelerated; its influence was multifaceted: (1) coupled with the radial secondary flow, it enhanced the wake vortex stretching and exhaustion near the hub; (2) it further increased the radial inclination of the wakes and the spacing between the adjacent wake vortices, resulting in the delay of wake vortex dissipation in the middle-upper area of the AITD channel; (3) it elongated and narrowed the wake vortex band (by as much as 40%). In the high \(f\) cases, the accelerated wake diffusion enhanced the turbulence intensity in the interval between the adjacent wakes, leading to an increase in the range of the high \(T_{u}\) region (up to 10%). The increasing \(T_{u}\) in the interval between the adjacent wakes could suppress the separation bubble size on the LPT-GV in advance before the wake center arrived, thereby reducing the separation loss. When the residual wake reached the LPT-GV, it could fully suppress the separation bubble within the scope of this paper. However, with increasing \(f\), the narrower wake vortex band reduced the radial range and time of its suppression effect, which undoubtedly increased the separation loss. Therefore, balancing the above two effects by adjusting the wake sweeping frequency was the key to reducing the LPT-GV separation loss. In comparison, the suppression of the wake with different sweeping frequencies on the separation bubble had little effect on the loss of the LPT-GV, while the influence on the passage vortices in the top area of the LPT-GV passage was the decisive factor affecting the change of the loss. At low \(f\), the enriched low-energy fluids around the casing thickened the boundary layer on the inlet end-wall of the LPT-GV and enhanced the passage vortices in the upper area; at high \(f\), although there was no accumulation of low-energy fluid around the casing, a large number of residual wake vortices near the LPT-GV inlet end-wall could also strengthen the passage vortices in the upper area. Therefore, there was an optimal \(f\) to minimize the total pressure loss caused by passage vortices. When \(f=1.34\), the influence of wake vortex interaction in the upper-middle regions of the AITD channel and wake vortex dissipation near the hub could be well balanced so that the loss of the AITD was minimized. For the LPT-GV,\(f=0.90\) is the optimal \(f\) within the scope of this paper, since the sweeping wakes with this\(f\) could minimize the total pressure loss caused by the passage vortices in the upper channel of the LPT-GV. For the integrated  
Figure 11: Total pressure loss for the all cases. AITD, the LPT-GV was the largest loss source (accounting for >80%), but the trend of its total pressure loss was basically consistent with that of the AITD, which also reached a minimum when \(f\) = 1.34. Conceptualization, Z.L. ; validation, S.S. and G.L. ; formal analysis, H.L. and X.O. ; writing--original draft preparation, Z.L. ; writing--review and editing, S.S. and G.L. ; supervision, Y.Z., X.L., G.X. and J.Z. All authors have read and agreed to the published version of the manuscript. This research was funded by the National Natural Science Foundation of China (grant number 51906242) and the National Science and Technology Major Project (grant numbers J2019-II-0007-0027 and J2019-III-0020-0064). Not applicable. The authors declare no conflict of interest.