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Title: Reynolds number effects on three-dimensional vorticity in a turbulent wake
Authors: Yiu, MW
Zhou, Y
Zhou, T
Cheng, L 
Issue Date: 2004
Source: AIAA Journal, 2004, v. 42, no. 5, p. 1009-1016
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 fluid) varies from 10 3 to 10 4, there is a large change in the turbulent near-wake dynamics (e.g., the base pressure coefficient, fluctuating lift coefficient, and vortex formation length) of a circular cylinder, which has 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 the vorticity vector and to provide a relatively complete set of three-dimensional vorticity data. All three components of vorticity were simultaneously measured in the intermediate region of a turbulent circular-cylinder wake using a multiwire vorticity probe. It is observed that the root-mean-square values of the three vorticity components increase with Re, especially the streamwise component, which shows a large jump from Re - 5×10 3 to Re = 10 4. At Re = 2.5×10 3, the maximum phase-averaged spanwise vorticity variance 〈ω z 2〉*, normalized by d and U ∞, is twice as large as its counterpart for the streamwise component, 〈ω x 2〉*, or the lateral component, 〈ω y 2〉*. However, at Re = 10 4, the maximum 〈ω z 2〉* is only 55% larger than the maximum 〈ω z 2〉 * or 47% larger than the maximum 〈ω y 2〉*. The observation is consistent with the perception that the three-dimensionality of the flow is enhanced at higher Re due to the occurrence of Kelvin-Helmholtz vortices. The effect of Re on vorticity signals, spectra, and coherent and incoherent vorticity fields is also examined.
Publisher: American Institute of Aeronautics and Astronautics
Journal: AIAA journal 
ISSN: 0001-1452
EISSN: 1533-385X
DOI: 10.2514/1.975
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