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High-speed stereo DPIV measurement of wakes of two bat species flying freely in a wind tunnel

Hedenström, Anders LU ; Muijres, Florian LU ; von Busse, R.; Johansson, L. C.; Winter, Y. and Spedding, G. R. (2009) In Experiments in Fluids 46(5). p.923-932
Abstract
Previous studies on wake flow visualization of live animals using DPIV have typically used low repetition rate lasers and 2D imaging. Repetition rates of around 10 Hz allow similar to 1 image per wingbeat in small birds and bats, and even fewer in insects. To accumulate data representing an entire wingbeat therefore requires the stitching-together of images captured from different wingbeats, and at different locations along the wing span for 3D-construction of wake topologies. A 200 Hz stereo DPIV system has recently been installed in the Lund University wind tunnel facility and the high-frame rate can be used to calculate all three velocity components in a cube, whose third dimension is constructed using the Taylor hypothesis. We studied... (More)
Previous studies on wake flow visualization of live animals using DPIV have typically used low repetition rate lasers and 2D imaging. Repetition rates of around 10 Hz allow similar to 1 image per wingbeat in small birds and bats, and even fewer in insects. To accumulate data representing an entire wingbeat therefore requires the stitching-together of images captured from different wingbeats, and at different locations along the wing span for 3D-construction of wake topologies. A 200 Hz stereo DPIV system has recently been installed in the Lund University wind tunnel facility and the high-frame rate can be used to calculate all three velocity components in a cube, whose third dimension is constructed using the Taylor hypothesis. We studied two bat species differing in body size, Glossophaga soricina and Leptonycteris curasoa. Both species shed a tip vortex during the downstroke that was present well into the upstroke, and a vortex of opposite sign to the tip vortex was shed from the wing root. At the transition between upstroke/downstroke, a vortex loop was shed from each wing, inducing an upwash. Vorticity iso-surfaces confirmed the overall wake topology derived in a previous study. The measured dimensionless circulation, I"/Uc, which is proportional to a wing section lift coefficient, suggests that unsteady phenomena play a role in the aerodynamics of both species. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Experiments in Fluids
volume
46
issue
5
pages
923 - 932
publisher
Springer
external identifiers
  • wos:000265880700014
  • scopus:67349228046
ISSN
1432-1114
DOI
10.1007/s00348-009-0634-5
language
English
LU publication?
yes
id
d92bb662-5858-4af3-bafa-55c24d3f07e2 (old id 1426355)
date added to LUP
2009-06-29 15:47:03
date last changed
2017-06-25 03:43:51
@article{d92bb662-5858-4af3-bafa-55c24d3f07e2,
  abstract     = {Previous studies on wake flow visualization of live animals using DPIV have typically used low repetition rate lasers and 2D imaging. Repetition rates of around 10 Hz allow similar to 1 image per wingbeat in small birds and bats, and even fewer in insects. To accumulate data representing an entire wingbeat therefore requires the stitching-together of images captured from different wingbeats, and at different locations along the wing span for 3D-construction of wake topologies. A 200 Hz stereo DPIV system has recently been installed in the Lund University wind tunnel facility and the high-frame rate can be used to calculate all three velocity components in a cube, whose third dimension is constructed using the Taylor hypothesis. We studied two bat species differing in body size, Glossophaga soricina and Leptonycteris curasoa. Both species shed a tip vortex during the downstroke that was present well into the upstroke, and a vortex of opposite sign to the tip vortex was shed from the wing root. At the transition between upstroke/downstroke, a vortex loop was shed from each wing, inducing an upwash. Vorticity iso-surfaces confirmed the overall wake topology derived in a previous study. The measured dimensionless circulation, I"/Uc, which is proportional to a wing section lift coefficient, suggests that unsteady phenomena play a role in the aerodynamics of both species.},
  author       = {Hedenström, Anders and Muijres, Florian and von Busse, R. and Johansson, L. C. and Winter, Y. and Spedding, G. R.},
  issn         = {1432-1114},
  language     = {eng},
  number       = {5},
  pages        = {923--932},
  publisher    = {Springer},
  series       = {Experiments in Fluids},
  title        = {High-speed stereo DPIV measurement of wakes of two bat species flying freely in a wind tunnel},
  url          = {http://dx.doi.org/10.1007/s00348-009-0634-5},
  volume       = {46},
  year         = {2009},
}