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The motion of a cavity in a vertical rotating tube

Published online by Cambridge University Press:  29 March 2006

R. Collins
Affiliation:
Department of Mechanical Engineering, University College London
M. T. Hoath
Affiliation:
Department of Mechanical Engineering, University College London

Abstract

Experiments are performed to measure the upward velocity U of the cavity resulting from the draining of a vertical liquid-filled tube of radius b, which rotates about its axis at various speeds. With no rotation the cavity moves so that the Froude number U/(gb)½ is constant, where g is the gravitational acceleration. For high angular velocities Ω, however, the cavity appears to adopt a constant value of the Rossby number Ub, implying that gravitational forces are dominaked by centrifugal forces. The cavity velocity finally achieved is found to be the same as the maximum group velocity of infinitesimal waves, so that Ub = 0.52. Approximate theoretical models which satisfactorily describe the development of the motion are constructed.

Type
Research Article
Copyright
© 1973 Cambridge University Press

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