Structure and flow patterns in turbulent wakes
作者:
Francesc Giralt,
J. A. Ferre´,
期刊:
Physics of Fluids A
(AIP Available online 1993)
卷期:
Volume 5,
issue 7
页码: 1783-1789
ISSN:0899-8213
年代: 1993
DOI:10.1063/1.858853
出版商: AIP
数据来源: AIP
摘要:
A pattern recognition technique is used to detect and identify patterns and structures embedded in the velocity field of a turbulent wake behind a cylinder. Two component velocitiesuand &ngr; oruandware measured with eight X‐wire anemometers aligned with the vertical and spanwise directions in the wake atx/D=420 and Re=1600. The velocity patterns educed as averaged patterns or instantaneous structures are consistent with the presence of double‐roller eddies, whose legs are continuously stretched by the rate of strain. Experimentaluand &ngr; data suggest that the rollers are connected at the top, with vorticity parallel to the cylinder axis, forming a horseshoe vortex. The fine‐scale activity, estimated by the envelope of the second derivatives, with respect to time of the velocity signals, confirms that this kind of structure can account for both theu&ngr; correlation and the continuous entrainment of potential flow into the wake.
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