非定常尾迹控制叶栅分离研究

本文采用大涡模拟对某大转角叶栅的非定常分离流动及其在非定常尾迹作用下的分离控制机理进行了数值分析。主要捕捉了两个特征频率:分离泡不稳定频率f_shear和尾缘脱落涡频率f_shed,研究了不同的激励频率、尾迹移动方向、随机脉动等激励特征控制流动分离的效果。结果显示:特定外部频率强化了分离剪切层中的K-H展向涡结构,f_shed能同时影响分离区域和尾涡区域,f_shear只能作用于分离区域;尾迹从吸力面向压力面移动时,分离结构表现出对来流周期性更明显的响应;进口随机脉动对破坏K-H展向涡结构非常有效。

Analysis of Controlling Separated Flow on Cascade by Unsteady Wake

The numerical analysis of unsteady separated flow on the large turning angle axial cascade and separation control mechanism suffered from unsteady incoming wake excitation has been carried out by large eddy simulation.Two characteristic frequencies,including f_shear of separation bubble unstable frequency and f_shed of trailing shedding vortex frequency,have been obtained.The different separation control effects have been analysed from the different external exciting characteristics, including different exciting frequencies,different wake moving directions,random velocity fluctuation, and so on.The results have shown that the specific external frequency will promote the formation of K-H spanwise vortices,and f_shed can affect the separation area and trailing vortex area,f_shear only can act on the separation area.Moving from suction surface to pressure surface,the response of separation structures from periodic incoming wake is more obvious.In addition,random velocity fluctuation will clearly redound to destroy the K-H spanwise vortex structures.