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.
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Abbreviations
- U o :
-
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
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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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Jang, Y.I., Lee, S.J. PIV analysis of near-wake behind a sphere at a subcritical Reynolds number. Exp Fluids 44, 905–914 (2008). https://doi.org/10.1007/s00348-007-0448-2
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DOI: https://doi.org/10.1007/s00348-007-0448-2