Analysis of the Unsteady Flow in Compressor Cascade With POD Method

Abstract

The leading edge vortex’s frequency characteristics and flow separation due to adverse pressure gradient are found to be dominant in the determination of compressor performance. For deep understanding of the unsteady gas flow in compressor cascade, the numerical study with Proper Orthogonal Decomposition (POD) reconstructed method is performed in the present study. And, the Fast Fourier Transform (FFT) is implemented to get the vortex fluctuation frequency to fully understand flow separation. Furthermore, the comparisons between the baseline results and the reconstructed flow field by POD method are conducted for investigating the feasibility of POD method. It demonstrated that a few POD modes are adequate to reconstruct main flow field and higher POD modes reflect more detailed flow structure. And also, the characteristic of mode coefficient is analyzed with the detailed explanations of POD. Then, the POD method, which decouples flow field in space and time, is found to be effective in the depiction of the vortex structure and the representation of the flow mechanism. The present study can be regarded as the first step to determine the number of POD modes and evaluates the error of reconstructed flow field.