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Wake-mediated synchronization and drafting in coupled flags

Published online by Cambridge University Press:  16 November 2009

SILAS ALBEN
SILAS ALBEN*
Affiliation:
School of Mathematics, Georgia Institute of Technology, Atlanta, GA 30332-0160, USA
*
†Email address for correspondence: [email protected]
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Abstract

A recent experiment has shown ‘inverted drafting’ in flags: the drag force on one flag is increased by excitation from the wake of another. Here we use vortex sheet simulations to show that inverted drafting occurs when the flag wakes add coherently to form strong vortices. By contrast, normal drafting occurs for higher frequency oscillations, when the vortex wake becomes more complex and mixed on the scale of the flag. The types of drafting and dynamics (synchronization and erratic flapping) depend on the separation distance between the flags. For both tandem and side-by-side flags in synchronized flapping, the phase difference depends nearly monotonically on separation distance.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 641 , 25 December 2009 , pp. 489 - 496
Copyright
Copyright © Cambridge University Press 2009

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