In order to analyze the characteristics of coherent structures of unsteady flow in a cascade separation flow

the large eddy simulation of single channel cascade with three different attack angles was carried out. Moreover

dynamic mode decomposition was made to analyze the inherent structures of the three different operations. With DMD(dynamic mode decomposition) method

the complex temporal-spatial flow fields can be decoupled and the coherent structures of different frequencies and scales can be captured. Besides

the main frequencies and their structures can be got to reflect the main dynamic behavior. Moreover

with DMD method

thousands of different flow fields can be expressed by low dimension of only dozens of modes. With the application of DMD method

the results showed that instability shear vortex was generated by flow separation of the leading edge of the cascade

coupling with the shedding vortex in the wake zone

producing new coherent structure. When the attack angle became larger

the shear vortex and its interaction with shedding vortex were strengthened

making the flow field more complicated.