Vortical patterns behind a tapered cylinder oscillating transversely
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Triantafyllou_1998_Vortical.pdf
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Author(s)
Techet, A. H.
Hover, F. S.
Triantafyllou, M.S.
Date Issued
1998
Publisher
Cambridge University Press
Citation
Journal of Fluid Mechanics, 363, p.79-96 (1998)
Abstract
Visualization studies of the flow behind an oscillating tapered cylinder are performed
at Reynolds numbers from 400 to 1500. The cylinder has taper ratio 40:1 and is
moving at constant forward speed U while being forced to oscillate harmonically
in the transverse direction. It is shown that within the lock-in region and above
a threshold amplitude, no cells form and, instead, a single frequency of response
dominates the entire span. Within certain frequency ranges a single mode dominates
in the wake, consisting of shedding along the entire span of either two vortices per
cycle (`2S' mode), or four vortices per cycle (`2P' mode); but within specific parametric
ranges a hybrid mode is observed, consisting of a `2S' pattern along the part of the
span with the larger diameter and a `2P' pattern along the part of the span with the
smaller diameter. A distinct vortex split connects the two patterns which are phaselocked
and have the same frequency. The hybrid mode is periodic, unlike vortex
dislocations, and the location of the vortex split remains stable and repeatable, within
one to two diameters, depending on the amplitude and frequency of oscillation and
the Reynolds number.
Subjects
vorticity
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
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This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.
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