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Title: Wavelet analysis of reynolds number effect on 3-D vorticity in a turbulent near wake
Authors: Yiu, MW
Li, H
Zhou, Y
Keywords: Turbulence
Reynolds number
Issue Date: 2003
Source: Proceedings of the ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference, Honolulu, Hawaii, USA, July 6–10, 2003, v. 1, paper no. FEDSM2003-45025, p. 231-236 How to cite?
Abstract: When Reynolds number, Re (≡U∞ d/v, where U∞ is the free stream velocity, d is the cylinder diameter and v is the kinematic viscosity of the fluid), is in the range of 103 to 104 , there is a large variation in the near-wake formation region in terms of the base pressure coefficient, the fluctuating lift coefficient, the vortex formation length, which have previously been connected to the generation of small-scale Kelvin-Helmholtz vortices. This work aims to investigate how this Re variation affects the three components of vorticity in terms of time-averaged and small-scale structures and also to provide a relatively complete set of 3-D vorticity data. All three components of vorticity data were simultaneously measured in the intermediate region of the turbulent wake using a multi-wire vorticity probe. It is observed that the root-mean-square (rms) values of the three vorticity components increase with Re, especially the streamwise component, which shows a large jump from Re = 5×103 to 104 . At the central frequencies of f0 and 2f0 , the contributions from the large-scale and intermediate-scale structures of ωzi 2 /(ωz 2 ) max decreases 13% and 16% respectively as the Re. increases. However, at the central frequency of 16f0 , the contribution of the small-scale structure of ωzi 2 /(ωz 2 ) max dramatic suddenly 7% increase at Re = 5×103 to 104 . The result suggest the generation of small-scale Kelvin-Helmholtz vortices in the spanwise structure. The effect of Re on vorticity signals, spectra, contributions from the wavelet components to the vorticity variances are also examined.
ISBN: 0-7918-3697-5
0-7918-3673-8 (E-ISBN)
DOI: 10.1115/FEDSM2003-45025
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