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Vortex interaction with a moving sphere

Published online by Cambridge University Press:  31 August 2007

J. J. ALLEN ,
Y. JOUANNE  and
B. N. SHASHIKANTH
J. J. ALLEN
Affiliation:
Department of Mechanical Engineering, New Mexico State University, NM, USA
Y. JOUANNE
Affiliation:
Department of Mechanical Engineering, l'Ecole Polytechnique, Université de Nantes, France
B. N. SHASHIKANTH
Affiliation:
Department of Mechanical Engineering, New Mexico State University, NM, USA
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Abstract

This paper details the experimental results of the axisymmetric collision of a vortex ring with a sphere. The experiments were conducted in water and a neutrally buoyant sphere was free to move in response to the impulse delivered by the vortex ring during the interaction. Good agreement has been achieved between kinematic data for the sphere speed and acceleration and the behaviour of the moment and rate of change of the moment of vorticity, measured using particle image velocimetry (PIV). The interaction of the vortex ring with the sphere creates secondary vorticity on the sphere surface. This initially results in a reduction of the fluid impulse and an acceleration of the sphere. However, within the measurement window of the interaction, the rate of increase of the positive moment of vorticity is slightly larger than the rate of increase of the negative moment of vorticityand the sphere gradually slows. A movie is available with the online version of the paper.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 587 , 25 September 2007 , pp. 337 - 346
Copyright
Copyright © Cambridge University Press 2007

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References

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Allen et al. supplementary movie

Movie 1. Interaction of vortex ring with a moving sphere. The visualizations were achieved using fluorescent dye in water and an argon-ion laser. The movie shows the ring deforming as it approaches the sphere. As the vortex passes around the sphere, significant secondary vorticity is generated on the surface of the sphere, which separates and evolves around the primary ring. As the vortex ring passes over the sphere secondary vorticity is deposited in its wake as what appears to be a second vortex ring.

Download Allen et al. supplementary movie(Video)
Video 767.1 KB

Allen et al. supplementary movie

Movie 1. Interaction of vortex ring with a moving sphere. The visualizations were achieved using fluorescent dye in water and an argon-ion laser. The movie shows the ring deforming as it approaches the sphere. As the vortex passes around the sphere, significant secondary vorticity is generated on the surface of the sphere, which separates and evolves around the primary ring. As the vortex ring passes over the sphere secondary vorticity is deposited in its wake as what appears to be a second vortex ring.

Download Allen et al. supplementary movie(Video)
Video 8.9 MB