Streamwise evolution of an inclined cylinder wake

Streamwise evolution of an inclined cylinder wake The streamwise evolution of an inclined circular cylinder wake was investigated by measuring all three velocity and vorticity components using an eight-hotwire vorticity probe in a wind tunnel at a Reynolds number Red of 7,200 based on free stream velocity (U ∞) and cylinder diameter (d). The measurements were conducted at four different inclination angles (α), namely 0°, 15°, 30°, and 45° and at three downstream locations, i.e., x/d = 10, 20, and 40 from the cylinder. At x/d = 10, the effects of α on the three coherent vorticity components are negligibly small for α ≤ 15°. When α increases further to 45°, the maximum of coherent spanwise vorticity reduces by about 50%, while that of the streamwise vorticity increases by about 70%. Similar results are found at x/d = 20, indicating the impaired spanwise vortices and the enhancement of the three-dimensionality of the wake with increasing α. The streamwise decay rate of the coherent spanwise vorticity is smaller for a larger α. This is because the streamwise spacing between the spanwise vortices is bigger for a larger α, resulting in a weak interaction between the vortices and hence slower decaying rate in the streamwise direction. For all tested α, the coherent contribution to $$ \overline{{v^{2}}} $$ is remarkable at x/d = 10 and 20 and significantly larger than that to $$ \overline{{u^{2}}} $$ and $$ \overline{{w^{2}}}. $$ This contribution to all three Reynolds normal stresses becomes negligibly small at x/d = 40. The coherent contribution to $$ \overline{{u^{2}}} $$ and $$ \overline{{v^{2}}} $$ decays slower as moving downstream for a larger α, consistent with the slow decay of the coherent spanwise vorticity for a larger α. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experiments in Fluids Springer Journals

Streamwise evolution of an inclined cylinder wake

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Publisher
Springer-Verlag
Copyright
Copyright © 2011 by Springer-Verlag
Subject
Engineering; Engineering Fluid Dynamics; Engineering Thermodynamics, Heat and Mass Transfer; Fluid- and Aerodynamics
ISSN
0723-4864
eISSN
1432-1114
D.O.I.
10.1007/s00348-011-1068-4
Publisher site
See Article on Publisher Site

Abstract

The streamwise evolution of an inclined circular cylinder wake was investigated by measuring all three velocity and vorticity components using an eight-hotwire vorticity probe in a wind tunnel at a Reynolds number Red of 7,200 based on free stream velocity (U ∞) and cylinder diameter (d). The measurements were conducted at four different inclination angles (α), namely 0°, 15°, 30°, and 45° and at three downstream locations, i.e., x/d = 10, 20, and 40 from the cylinder. At x/d = 10, the effects of α on the three coherent vorticity components are negligibly small for α ≤ 15°. When α increases further to 45°, the maximum of coherent spanwise vorticity reduces by about 50%, while that of the streamwise vorticity increases by about 70%. Similar results are found at x/d = 20, indicating the impaired spanwise vortices and the enhancement of the three-dimensionality of the wake with increasing α. The streamwise decay rate of the coherent spanwise vorticity is smaller for a larger α. This is because the streamwise spacing between the spanwise vortices is bigger for a larger α, resulting in a weak interaction between the vortices and hence slower decaying rate in the streamwise direction. For all tested α, the coherent contribution to $$ \overline{{v^{2}}} $$ is remarkable at x/d = 10 and 20 and significantly larger than that to $$ \overline{{u^{2}}} $$ and $$ \overline{{w^{2}}}. $$ This contribution to all three Reynolds normal stresses becomes negligibly small at x/d = 40. The coherent contribution to $$ \overline{{u^{2}}} $$ and $$ \overline{{v^{2}}} $$ decays slower as moving downstream for a larger α, consistent with the slow decay of the coherent spanwise vorticity for a larger α.

Journal

Experiments in FluidsSpringer Journals

Published: Mar 24, 2011

References

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