This study used large eddy simulation (LES) to investigate the control mechanism of a fluidic oscillator in the suppression of non-reattachment separation of a boundary layer from an ultra-high-lift, aft-loaded, low-pressure turbine under low Reynolds number. The internal flow characteristics of the fluidic oscillator were examined, with a focus on the influence mechanism of the pulse jet from the fluidic oscillator on boundary layer separation and transition. The effects of different jet angles (θ) on the suppression of separation bubbles were also compared in detail. Finally, the mechanism of interaction between the fluidic oscillator jet and the blade suction surface boundary layer was assessed. It was found that the pulse jet of the fluidic oscillator generated a streamwise vortex pair above the surface of the blade suction, which promoted an exchange of momentum between the boundary layer for the blade suction surface and the main flow, and clearly suppressed boundary layer separation. The streamwise vortex pair at $\theta =30$° showed the characteristics of higher strength, smaller size, slower decay, and longer penetration distance than the results at $\theta =90$°, such that the momentum exchange between the low-energy fluid inside the boundary layer and the main flow is sustainable, which promoted the laminar boundary layer to produce bypass transition and significantly improved the aerodynamic performance of the turbine.

本研究使用大涡模拟 (LES) 来研究流体振荡器在低雷诺数下抑制超高升力、后载低压涡轮机边界层非再附着分离的控制机制. 研究了流体振荡器的内部流动特性，重点研究了流体振荡器脉冲射流对边界层分离和过渡的影响机制。不同射流角度的影响 ( θ)对分离气泡的抑制也进行了详细比较。最后，评估了流体振荡器射流与叶片吸力表面边界层之间的相互作用机制。发现流体振荡器的脉冲射流在叶片吸力面上方产生一个流向涡对，促进了叶片吸力面边界层与主流之间的动量交换，明显抑制了边界层分离. 流向涡对在$\theta =30$° 表现出强度更高、尺寸更小、衰减更慢、穿透距离更长的特点。 $\theta =90$°，使得边界层内的低能流体与主流之间的动量交换是可持续的，促进了层流边界层产生旁路过渡，显着提高了涡轮的气动性能。