Abstract: In order to research the unsteady flow pattern of the tip clearance flow in a low velocity isolated compressor cascade， LES was used in numerical simulation of the flow field， Dynamic Mode Decomposition(DMD) was conducted to analyze the velocity field of tip secondary flow in section S3 at x/c=1.0677 chord length. The results showed that DMD was able to extract the steady mode and the main oscillation feature with different frequencies from original velocity fields. Meanwhile， the velocity dynamic modes fully revealed that， the first mode oscillation with lower frequency f1=824.9Hz was caused by the generation and fade of the tip leakage vortex， and the instability of moving end-wall shear layer gave rise to the second mode oscillation with higher frequency f2=9807.2Hz which reflected in the oscillation and division of the tip leakage vortices.

Key words: Dynamic mode decomposition；Tip clearance flow；Tip leakage vortex；Moving end-wall

摘要： 为了研究低速孤立压气机叶栅叶顶间隙流的非定常运动型态，采用大涡模拟 (LES) 技术对流场进行数值模拟，并运用动力学模态分解 (DMD) 技术对x/c=1.0677弦长处S3截面叶顶二次流速度场进行模态分析。结果表明:动力学模态分解 (DMD) 能够得到速度场的定常模态和不同频率下的主要振荡特征。同时揭示了频率为f1=824.9Hz的一阶振荡主要表现为泄漏涡的低频周期性生成与退化；而频率为f2=9807.2Hz的二阶振荡是由叶顶移动端壁形成剪切层内的不稳定造成的，主要表现为泄漏涡的振荡与分裂。

关键词: 动力学模态分解；叶顶间隙流；叶顶泄漏涡；移动端壁