周期性低频尾迹对边界层演变影响的瞬态研究

Transient research on the influence of the periodic low-frequency wake on the boundary layer evolution

为了加深对压气机静叶吸力面的流动分离研究与理解,本文使用URANS模型瞬态模拟扰流棒产生的周期性低频尾迹来流与平板表面的流动分离转捩之间的交互作用。在平板前缘约3%自由流湍流度,进口雷诺数70000的条件下,通过计算折合频率f+=0.5对应的平板表面流动状态,揭示了低频来流尾迹与分离剪切层内部运动之间的交互作用。结果表明:来流尾迹导致边界层分离点略微提前,同时由于周期性的移动而没有确定的再附着点。尾迹能量输入导致分离泡被压缩拉长是分离泡抑制的具体过程,大约持续0.125个扰流棒周期。分离转捩区内高能震荡区在x/L=0.65左右,约为180~200 Hz。本文流场环境条件下,流向条纹Kelvin-Helmholtz不稳定性和尾迹振荡能量的输入共同导致了边界层的转捩,其间未见明显的Tollmien-Schlichting不稳定性。

To deepen the research and understanding of the flow separation on the suction surface of a compressor vane,in this study,the unsteady Reynolds-averaged Navier Stokes model is used to simulate the interaction between the periodic low-frequency incoming wake generated by a spoiler and flow separation transition on the plate surface.With approximately 3%free-stream turbulence at the front edge of the plate and an inlet Reynolds number of 70000,the flow state of the plate surface corresponding to a reduced frequency f of 0.5 is calculated.The results reveal the interaction between the low-frequency incoming wake and the internal motion of the separating shear layer in detail.The results show that the incoming wake causes the boundary layer separation point to slightly advance and that there is no definite reattachment point due to periodic movements.The wake energy input causes the separation bubble to be compressed and elongated,which is the specific process of separation bubble suppression with a moving period lasting approximately 0.125 bars.The high-energy oscillation zone in the separation transition zone is at approximately x/L=0.65,with a frequency of approximately 180~200 Hz.Under the conditions of the flow field introduced in this paper,the inputs of the streamwise streak,Kelvin-Helmholtz instability,and wake oscillation energy led to the transition of the boundary layer together,during which no obvious Tollmien-Schlichting instability was observed.