Three-dimensional flow structures and vorticity control in fish-like swimming
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Triantafyllou_2002_Three.pdf
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Author(s)
Zhu, Q.
Wolfgang, M.J.
Yue, D.K.P.
Triantafyllou, M.S.
Date Issued
2002
Publisher
Cambridge University Press
Citation
Journal of Fluid Mechanics, 468, p.1-28 (2002)
Abstract
We employ a three-dimensional, nonlinear inviscid numerical method, in conjunction
with experimental data from live fish and from a fish-like robotic mechanism, to
establish the three-dimensional features of the flow around a fish-like body swimming
in a straight line, and to identify the principal mechanisms of vorticity control
employed in fish-like swimming. The computations contain no structural model for
the fish and hence no recoil correction. First, we show the near-body flow structure
produced by the travelling-wave undulations of the bodies of a tuna and a giant
danio. As revealed in cross-sectional planes, for tuna the flow contains dominant
features resembling the flow around a two-dimensional oscillating plate over most
of the length of the fish body. For the giant danio, on the other hand, a mixed
longitudinal-transverse structure appears along the hind part of the body. We also
investigate the interaction of the body-generated vortices with the oscillating caudal
fin and with tail-generated vorticity. Two distinct vorticity interaction modes are
identified: the first mode results in high thrust and is generated by constructive
pairing of body-generated vorticity with same-sign tail-generated vorticity, resulting
in the formation of a strong thrust wake; the second corresponds to high propulsive
efficiency and is generated by destructive pairing of body-generated vorticity with
opposite-sign tail-generated vorticity, resulting in the formation of a weak thrust
wake.
Subjects
flow structures
vorticity control
fish-like
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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