###### Abstract  
A dynamic simulation was launched to research the influence of high-pressure turbine (HPT) rotor wake passing frequency on the flow mechanism in an integrated aggressive interturbine duct (AITD). Sweeping rods were adopted to replace the HPT rotors to decouple the influence of its wake from those of other secondary flows. The diameter of the rods (d/s, nondimensionalized by the pitch (s) of the integrated struts at midspan) was 0.10, and their reduced frequency (\(f\)) ranged from 0.49 to 1.61. The k-\(\omega\) SST turbulence model and \(\gamma\)-\(\theta\) transition model were adopted for the turbulence closure. A 6.3-million-node structured grid was used to meet the grid dependency. Along with increasing \(f\), the intensified circumferential motion of the wake (1) enhances the wake vortex stretching and exhaustion near the hub; (2) promotes the radial inclination of wakes and elongates and narrows the wake vortex band, resulting in increased spacing between the adjacent wake vortices and the weakened vortex interaction. In the high-\(f\) cases, the enhanced turbulence intensity in the interval between the adjacent wakes could suppress the separation bubble on LPT-GV in advance, but the elongated and narrowed wake vortices resulted in a substantial reduction in the radial extent and duration of their suppression on the separation bubble. Therefore, the influence of \(f\) on the integrated AITD and its parts was bidirectional, and adjusting the sweeping frequency to balance its positive and negative effects could minimize the total loss in the integrated AITD. interturbine transition duct; sweeping rods; boundary layer transition; unsteady flow +
Footnote †: journal: Medicaldeveloped into a vortex pair around the shroud. [PERSON] et al. [4] attributed the main loss sources in ITDs to the radial movement and flow mixing between the mid-passage and casing. [PERSON] et al. [5] found that the greater area ratio and mean rise angle aggravated the inverse streamwise pressure gradient and the separation bubble on the casing. [PERSON] [6] and [PERSON] [7] found that the negative effect of the large rising angle could be offset by modifying LPT vanes. [PERSON] et al. [8] indicated that the change of curvature and expansion rate, resulting from the shortening non-dimensional length, was the primary factor influencing the secondary flow in ITDs. Along with the inlet swirl, the increased effective motion path of the fluid decreased the pressure gradient on the wall, resulting in inhibition of the flow separation on the casing [9; 10; 11]. Along with the increasing tip clearance of the HPT blades, the swirling flow around the casing was enhanced at the ITD inlet, which was conducive to the inhibition of the flow separation on the casing [12; 13; 14]. However, the greater tip clearance caused more total pressure loss in ITD. [PERSON] et al. [15] proposed that there is a circumferential location of the LPT-GV for optimizing the effect of its potential flow and maximizing aerodynamic performance for a particular ITD. [PERSON] [16] found that the divergence of the flow channel initiated by the struts deteriorated the flow separation and the nonsteady flow significantly, resulting in loss augmentation. The design concept of struts integrated in ITD, proposed by [PERSON] et al. [17], could improve the flow quality at the integrated ITD outlet and also reduce the strut weight by 20-39%. The aggravated outlet flow uniformity of the integrated ITD [18] could be improved by adding two splitter blades with zero-loading between the adjacent struts, as the splitter blades divided the large passage vortices into small ones [19; 20]. However, the flow homogeneity at the outlet was improved at the price of the total pressure loss augmentation. [PERSON] [21] and [PERSON] [22] indicated that the convergence channel of the wide-chord strut changed the pressure gradient in the radial and circumferential direction in the integrated AITD, which was conducive to suppressing the flow separation on the shroud and reducing the flow loss.