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Turbulent vortex rings

Published online by Cambridge University Press:  29 March 2006

T. Maxworthy
T. Maxworthy
Affiliation:
Departments of Aerospace and Mechanical Engineering, University of Southern California, Los Angeles, California 90007
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Abstract

We consider the motion of the mass of fluid ejected through a sharp-edged orifice by the motion of a piston. The vorticity formed by viscous forces within the separated flow at the sharp edge rolls up to form a concentrated vortex which, after a development period, consists of a core of very fine scale turbulence surrounded by a co-moving bubble of much larger scale turbulence. This bubble entrains outer fluid, mixes with it, and deposits the majority into a wake together with some small fraction of the total vorticity of the ring. Enough fluid is retained to account for the slow growth of the whole fluid mass. A theory which takes account of both the growth process and the loss of vorticity is proposed. By comparison with experimental measurements we have determined that the entrainment coefficient for turbulent vortex rings has a value equal to 0.011 ± 0.001, while their effective drag coefficient is 0.09 ± 0.01. These results seem to be independent of Reynolds number to within experimental accuracy.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 64 , Issue 2 , 19 June 1974 , pp. 227 - 240
Copyright
© 1974 Cambridge University Press

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Footnotes

With an appendix on an extended theory of laminar vortex rings.

References

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