Volume 38, Number 1, February 2020
|Page(s)||121 - 129|
|Published online||12 May 2020|
Comparative Study on Modal Decomposition Methods of Unsteady Separated Flow in Compressor Cascade
School of Power and Energy, Northwestern Polytechnical University, Xi'an 710072, China
2 Yangtze River Delta Research Institute of Northwestern Polytechnical University, Taicang 215400, China
3 Beijing Changcheng Institute of Metrology and Measurement, Beijing 100095, China
The present work investigated the vortex structure and fluctuation frequency characteristics generated by boundary layer separation of a high-load compressor cascade using modal decomposition methods. The dominant modes and dynamic behaviors of unsteady flow in the cascade were obtained, and the differences of three modal decomposition methods (Proper Orthogonal Decomposition, Dynamic Mode Decomposition and Spectral Proper Orthogonal Decomposition) in feature recognition of cascade flow were discussed. The results show that:(1) The POD method can accurately extract the dominant spatial structure of the flow field, but the modal coefficients are multi-frequency coupled, which makes the dominant modal characteristics of cascade flow unclear. (2) The standard DMD method can obtain the spatial-temporal single frequency mode of cascade flow, as well as their growth rates and frequencies. However, this method is likely to capture the suboptimal mode of large amplitude with large attenuation rate, and fails to obtain the high-frequency coherent structure, which makes it impossible to obtain the dominant feature with limited mode number. (3) The SPOD method, based on spectral characteristics, can obtain spatial and temporal single frequency modes, and there is no modal screening problem. The use of spectral estimation method (SPOD) reduces the sensitivity to numerical noise. This method can obtain the low-rank behavior of cascade flow, which is helpful to understand cascade flow mechanisms. Therefore, SPOD method is more advantageous for the modal analysis of unsteady separated flow in high-load compressor cascade.
Key words: proper orthogonal decomposition / dynamic mode decomposition / spectral proper orthogonal decomposition / single frequency mode / cascade flow mechanisms
关键字 : 本征正交分解 / 动态模态分解 / 谱本征正交分解 / 单频模态 / 叶栅流动机理
© 2020 Journal of Northwestern Polytechnical University. All rights reserved.
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