Unsteady Flow Field Analysis of Axial Compressor Cascade Based on Proper Orthogonal Decomposition and Dynamic Mode Decomposition Methods

The analysis of the unsteady flow field in axial compressor cascade is conducted using methods such as proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD). Data on the unsteady flow field of the Stage-35 compressor cascade are acquired via computational fluid dynamics (CFD) simulations and subsequently processed using POD and DMD for dimensionality reduction. Using singular value decomposition, the POD technique identifies the dominant modes, showing that the first nine modes account for 99% of the energy in the flow field, thus highlighting the primary flow structures. On the other hand, the DMD approach isolates the periodic and high-frequency dynamics within the flow field by decomposing the dynamic modes, effectively identifying fine variations in the unsteady flow. The study examines the flow field at three distinct moments within an unsteady cycle, specifically at 1/4T, 1/2T, and 3/4T, reconstructing the flow field at each instance and performing root mean square error analysis. Reconstruction results and error analysis demonstrate that the POD method excels at reconstructing low-frequency features, whereas the DMD method accurately identifies the unsteady dynamic aspects of the flow field, excelling in resolving high-frequency details. Both methods demonstrate high feasibility regarding the accuracy and efficiency of flow field reconstruction.