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Vortex interactions with flapping wings and fins can be unpredictable.

Lentink, David; Van Heijst, Gertjan F; Muijres, Florian LU and Van Leeuwen, Johan L (2010) In Biology Letters 6(3). p.394-397
Abstract
As they fly or swim, many animals generate a wake of vortices with their flapping fins and wings that reveals the dynamics of their locomotion. Previous studies have shown that the dynamic interaction of vortices in the wake with fins and wings can increase propulsive force. Here, we explore whether the dynamics of the vortex interactions could affect the predictability of propulsive forces. We studied the dynamics of the interactions between a symmetrically and periodically pitching and heaving foil and the vortices in its wake, in a soap-film tunnel. The phase-locked movie sequences reveal that abundant chaotic vortex-wake interactions occur at high Strouhal numbers. These high numbers are representative for the fins and wings of... (More)
As they fly or swim, many animals generate a wake of vortices with their flapping fins and wings that reveals the dynamics of their locomotion. Previous studies have shown that the dynamic interaction of vortices in the wake with fins and wings can increase propulsive force. Here, we explore whether the dynamics of the vortex interactions could affect the predictability of propulsive forces. We studied the dynamics of the interactions between a symmetrically and periodically pitching and heaving foil and the vortices in its wake, in a soap-film tunnel. The phase-locked movie sequences reveal that abundant chaotic vortex-wake interactions occur at high Strouhal numbers. These high numbers are representative for the fins and wings of near-hovering animals. The chaotic wake limits the forecast horizon of the corresponding force and moment integrals. By contrast, we find periodic vortex wakes with an unlimited forecast horizon for the lower Strouhal numbers (0.2-0.4) at which many animals cruise. These findings suggest that swimming and flying animals could control the predictability of vortex-wake interactions, and the corresponding propulsive forces with their fins and wings. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Animal: physiology, Flight, Animal, Extremities: physiology, Extremities, Animals, Biomechanics, Models, Anatomic, Biological, Swimming, Swimming: physiology, Wing, Wing: physiology
in
Biology Letters
volume
6
issue
3
pages
394 - 397
publisher
Royal Society
external identifiers
  • scopus:77953043763
ISSN
1744-9561
DOI
10.1098/rsbl.2009.0806
language
English
LU publication?
yes
id
f970ce15-3d76-4ed9-a8a0-ee704fd61f30 (old id 1886273)
date added to LUP
2011-04-06 12:42:43
date last changed
2018-05-29 11:15:44
@article{f970ce15-3d76-4ed9-a8a0-ee704fd61f30,
  abstract     = {As they fly or swim, many animals generate a wake of vortices with their flapping fins and wings that reveals the dynamics of their locomotion. Previous studies have shown that the dynamic interaction of vortices in the wake with fins and wings can increase propulsive force. Here, we explore whether the dynamics of the vortex interactions could affect the predictability of propulsive forces. We studied the dynamics of the interactions between a symmetrically and periodically pitching and heaving foil and the vortices in its wake, in a soap-film tunnel. The phase-locked movie sequences reveal that abundant chaotic vortex-wake interactions occur at high Strouhal numbers. These high numbers are representative for the fins and wings of near-hovering animals. The chaotic wake limits the forecast horizon of the corresponding force and moment integrals. By contrast, we find periodic vortex wakes with an unlimited forecast horizon for the lower Strouhal numbers (0.2-0.4) at which many animals cruise. These findings suggest that swimming and flying animals could control the predictability of vortex-wake interactions, and the corresponding propulsive forces with their fins and wings.},
  author       = {Lentink, David and Van Heijst, Gertjan F and Muijres, Florian and Van Leeuwen, Johan L},
  issn         = {1744-9561},
  keyword      = {Animal: physiology,Flight,Animal,Extremities: physiology,Extremities,Animals,Biomechanics,Models,Anatomic,Biological,Swimming,Swimming: physiology,Wing,Wing: physiology},
  language     = {eng},
  number       = {3},
  pages        = {394--397},
  publisher    = {Royal Society},
  series       = {Biology Letters},
  title        = {Vortex interactions with flapping wings and fins can be unpredictable.},
  url          = {http://dx.doi.org/10.1098/rsbl.2009.0806},
  volume       = {6},
  year         = {2010},
}