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Experiments in Fluids

, Volume 44, Issue 6, pp 905–914 | Cite as

PIV analysis of near-wake behind a sphere at a subcritical Reynolds number

  • Young Il Jang
  • Sang Joon LeeEmail author
Research Article

Abstract

The vortical structure of near-wake behind a sphere is investigated using a PIV technique in a circulating water channel at Re = 11,000. The measured velocity fields show a detailed vortical structure in the recirculation region such as recirculation vortices, reversed velocity zone, and out-of-plane vorticity distribution. The vorticity distribution of the sphere wake shows waviness in cross-sectional planes. The time-averaged turbulent structures are consistent with the visualized flow showing the onset of shear layer instability. The spatial distributions of turbulent intensities provide turbulent statistics for validating numerical predictions.

Keywords

Vortex Vortical Structure Recirculation Region Instantaneous Velocity Field Shear Layer Instability 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols

Uo

free stream velocity

d

sphere diameter

Re

Reynolds number \( (U_{o} \cdot d/\nu) \)

V

mean velocity component

V′

fluctuation velocity component

ω

vorticity

(x, y, z)

Cartesian coordinate directions

\( {{\sqrt {\overline{{V^{{'2}}_{x} }} } }} \mathord{\left/ {\vphantom {{{\sqrt {\overline{{V^{{'2}}_{x} }} } }} {U_{o} }}} \right. \kern-\nulldelimiterspace} {U_{o} } \)

turbulence intensity of V x

\( {{\sqrt {\overline{{V^{{'2}}_{y} }} } }} \mathord{\left/ {\vphantom {{{\sqrt {\overline{{V^{{'2}}_{y} }} } }} {U_{o} }}} \right. \kern-\nulldelimiterspace} {U_{o} } \)

turbulence intensity of V y

\( {{\sqrt {\overline{{V^{{'2}}_{z} }} } }} \mathord{\left/ {\vphantom {{{\sqrt {\overline{{V^{{'2}}_{z} }} } }} {U_{o} }}} \right. \kern-\nulldelimiterspace} {U_{o} } \)

turbulence intensity of V z

Notes

Acknowledgments

This work was supported by the Korea Science and Engineering Foundation (KOSEF) through the National Research Lab. Program funded by the Ministry of Science and Technology (No. M10600000276-06J0000-27610).

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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringPohang University of Science and TechnologyPohangRepublic of Korea

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