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Leading edge vortices in lesser long-nosed bats occurring at slow but not fast flight speeds.

Muijres, Florian LU ; Johansson, Christoffer LU ; Winter, York and Hedenström, Anders LU (2014) In Bioinspiration & Biomimetics 9(2).
Abstract
Slow and hovering animal flight creates high demands on the lift production of animal wings. Steady state aerodynamics is unable to explain the forces required and the most commonly used mechanism to enhance the lift production is a leading edge vortex (LEV). Although LEVs increase the lift, they come at the cost of high drag. Here we determine the flow above the wing of lesser long-nosed bats at slow and cruising speed using particle image velocimetry (PIV). We find that a prominent LEV is present during the downstroke at slow speed, but not at cruising speed. Comparison with previously published LEV data from a robotic flapper inspired by lesser long-nosed bats suggests that bats should be able to generate LEVs at cruising speeds, but... (More)
Slow and hovering animal flight creates high demands on the lift production of animal wings. Steady state aerodynamics is unable to explain the forces required and the most commonly used mechanism to enhance the lift production is a leading edge vortex (LEV). Although LEVs increase the lift, they come at the cost of high drag. Here we determine the flow above the wing of lesser long-nosed bats at slow and cruising speed using particle image velocimetry (PIV). We find that a prominent LEV is present during the downstroke at slow speed, but not at cruising speed. Comparison with previously published LEV data from a robotic flapper inspired by lesser long-nosed bats suggests that bats should be able to generate LEVs at cruising speeds, but that they avoid doing so, probably to increase flight efficiency. In addition, at slow flight speeds we find LEVs of opposite spin at the inner and outer wing during the upstroke, potentially providing a control challenge to the animal. We also note that the LEV stays attached to the wing throughout the downstoke and does not show the complex structures found in insects. This suggests that bats are able to control the development of the LEV and potential control mechanisms are discussed. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Bioinspiration & Biomimetics
volume
9
issue
2
publisher
IOP Publishing
external identifiers
  • pmid:24855067
  • wos:000336804400007
  • scopus:84901425521
ISSN
1748-3190
DOI
10.1088/1748-3182/9/2/025006
project
CAnMove
language
English
LU publication?
yes
id
b603c50a-4987-44e9-b08a-26716243980c (old id 4452642)
date added to LUP
2014-06-19 13:37:01
date last changed
2017-10-01 03:16:16
@article{b603c50a-4987-44e9-b08a-26716243980c,
  abstract     = {Slow and hovering animal flight creates high demands on the lift production of animal wings. Steady state aerodynamics is unable to explain the forces required and the most commonly used mechanism to enhance the lift production is a leading edge vortex (LEV). Although LEVs increase the lift, they come at the cost of high drag. Here we determine the flow above the wing of lesser long-nosed bats at slow and cruising speed using particle image velocimetry (PIV). We find that a prominent LEV is present during the downstroke at slow speed, but not at cruising speed. Comparison with previously published LEV data from a robotic flapper inspired by lesser long-nosed bats suggests that bats should be able to generate LEVs at cruising speeds, but that they avoid doing so, probably to increase flight efficiency. In addition, at slow flight speeds we find LEVs of opposite spin at the inner and outer wing during the upstroke, potentially providing a control challenge to the animal. We also note that the LEV stays attached to the wing throughout the downstoke and does not show the complex structures found in insects. This suggests that bats are able to control the development of the LEV and potential control mechanisms are discussed.},
  articleno    = {025006},
  author       = {Muijres, Florian and Johansson, Christoffer and Winter, York and Hedenström, Anders},
  issn         = {1748-3190},
  language     = {eng},
  number       = {2},
  publisher    = {IOP Publishing},
  series       = {Bioinspiration & Biomimetics},
  title        = {Leading edge vortices in lesser long-nosed bats occurring at slow but not fast flight speeds.},
  url          = {http://dx.doi.org/10.1088/1748-3182/9/2/025006},
  volume       = {9},
  year         = {2014},
}