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Forces on cylinders in viscous oscillatory flow at low Keulegan-Carpenter numbers

Published online by Cambridge University Press:  20 April 2006

P. W. Bearman ,
M. J. Downie ,
J. M. R. Graham  and
E. D. Obasaju
P. W. Bearman
Affiliation:
Department of Aeronautics, Imperial College, London SW7 2BY
M. J. Downie
Affiliation:
Department of Aeronautics, Imperial College, London SW7 2BY
J. M. R. Graham
Affiliation:
Department of Aeronautics, Imperial College, London SW7 2BY
E. D. Obasaju
Affiliation:
Department of Aeronautics, Imperial College, London SW7 2BY
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Abstract

This paper presents a comparison between theory and experiment for the in-line forces on cylinders of general cross-section in planar oscillatory flows of small amplitude. The theoretical analysis evaluates corrections to the standard inviscid inertial force at low Keulegan-Carpenter numbers which arise from the presence of viscous laminar boundary layers and from the development of vortex shedding. The boundary-layer contribution due to both skin friction and displacement effects is calculated to first order in the Stokes parameter β−½. The contribution to the in-line force from separation and vortex shedding, for which the results presented only apply to sharp-edged bodies, is taken from previous work on vortex shedding from isolated edges using the discrete vortex modelling technique. The resulting force has components both in phase with the fluid acceleration (inertia) and in phase with the velocity (drag).

The theoretical results are compared to measurements taken in a [xcup ]-tube water channel on a number of cylinders of different cross-section including circular cylinders and sharp-edged sections. The comparisons suggest that the theory is valid for Keulegan–Carpenter numbers below about 3 and for moderately high values of the β parameter.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 154 , May 1985 , pp. 337 - 356
Copyright
© 1985 Cambridge University Press

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