期刊
OCEAN ENGINEERING
卷 264, 期 -, 页码 -出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.oceaneng.2022.112547
关键词
PIV; Wavelet; Wake flow; Proper orthogonal decomposition; Multi-scale
资金
- National natural Science Foundation of China [11802108, 52105260]
- Major Basic Research Project of the Natural Science Foundation of the Jiangsu Higher Education Institutions [19KJA510002]
- Science and Technology Project of Changzhou [52105260, CE20205036]
- research Fund of Key Laboratory of Unsteady Aerodynamics and Flow Control, MIIT, Nanjing University of Aeronautics and Astronautics [KLUAFC-E-202102]
- National natural Science Foun- dation of China [52105260]
- [CE20220066]
In this study, a hybrid two-dimensional orthogonal wavelet multiresolution and proper orthogonal decomposition technique is developed to analyze the wake flow behind a semi cylinder. The study investigates the modal energy distributions, flow patterns, and PSD distributions of multi-scale flow structures using the proposed technique. The results show the changes in dominance, symmetry, and energy distribution of the flow structures as they vary from large-scale to small-scale.
A hybrid two-dimensional orthogonal wavelet multiresolution and proper orthogonal decomposition technique is developed to analyze the wake flow behind a semi cylinder. The two-dimensional orthogonal wavelet analysis is first applied to decompose the measured velocity fields into four wavelet components based on their spatial scales. Then the extracted multi-scale structures are further investigated based on proper orthogonal decom-position. The modal energy distributions of multi-scale flow structures suggest that the dominance of first two POD modes is reduced and the relative energy becomes more distributed as the flow structure changes from large-scale to small-scale. The first two POD modes of intermediate-scale structure also appear in a mode pair and they are related to secondary resonance accompanied with large-scale flow oscillation. The POD mode 3 of intermediate-scale structure suggest the existence of symmetric vortex shedding pattern. The first two POD modes of small-scale structure also display a symmetrically distributed vortex pair and the distance between adjacent vortices is about half of the case of mode 3 of intermediate-scale structure. The PSD distributions of POD modes of multi-scale structures suggest that the bandwidth of PSD becomes less concentrated as the flow structure varies from large-scale to small-scale. Distinctive flow patterns associated with first and second order harmonics of fundamental flow oscillation can be successfully extracted from the dominating POD modes of intermediate-scale and small-scale structures. The proposed hybrid technique provides a tool for relate the most energetic flow events over a period of time with multi-scale structures cascaded in the turbulence flow.
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