POD analysis on the sphere wake at a subcritical Reynolds number |
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Authors: | Young Il Jang and Sang Joon Lee |
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Institution: | (1) Department of Aerospace and Mechanical Engineering, ROK Air Force Academy, Choongbuk, 363-840, Korea;(2) Department of Mechanical Engineering, Pohang University of Science and Technology, San 31, Hyo-Ja Dong, Pohang, 790-784, Korea; |
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Abstract: | Abstract Flow characteristics of turbulent wake behind a sphere at a subcritical flow regime were experimentally investigated. The
particle image velocimetry measurements and proper orthogonal decomposition (POD) modal analysis were employed to get detailed
flow information such as the wavy structure, swirling motion and coherent structures of the sphere wake. The variation of
turbulent intensities of the radial and circumferential velocity components showed the swirling motion of sphere wake in the
cross-sectional planes. The relative contribution of the POD mode 1, 2 and 3 in eigenvalues was 26, 11, and 8%, respectively.
The general pattern of velocity fields for the POD mode 1 in the near-wake region of x/d = 0.7–1.4 is similar with that of time-averaged mean velocity fields. In addition, the sweeping flow in the region from x/d = 1.5 to x/d = 2.0 possesses wavy structure of the sphere wake. The experimental results of the present study would contribute to the
fundamental understanding of the turbulent near-wake behind a sphere. |
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