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On vortex strength and drag in bluff-body wakes

Published online by Cambridge University Press:  29 March 2006

Owen M. Griffin  and
Steven E. Ramberg
Owen M. Griffin
Affiliation:
Naval Research Laboratory, Washington, D.C. 20375
Steven E. Ramberg
Affiliation:
Naval Research Laboratory, Washington, D.C. 20375
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Abstract

In a recent paper (Griffin & Ramberg 1974) the authors studied the vortex-street wakes behind forced vibrating rigid cylinders. All experimental conditions were within the regime of wake capture or synchronization between the vibration and vortex frequencies. Both mean and fluctuating velocities in the wake together with the length of the vortex formation region were measured as functions of vibration amplitude and frequency at a Reynolds number of 144. The viscous vortex strength, age and spacing at this Reynolds number were then obtained by matching a model for the vortex street with the mean and r.m.s. velocity profiles obtained from hot-wire measurements. These results are employed here to determine the steady drag force on the vibrating cylinder by means of the von Kármán drag formulation. The drag coefficients determined in this way are in agreement with the recently published direct force measurements of Tanida, Okajima & Watanabe (1973) and Griffin, Skop & Koopmann (1973) at Reynolds numbers of 80, 500-900 and 4000. From these results a direct relation is drawn between the increased drag on resonantly vibrating structures and changes in the vortex strength, spacing and formation in their wakes.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 69 , Issue 4 , 24 June 1975 , pp. 721 - 728
Copyright
© 1975 Cambridge University Press

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References

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