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The implications of low-speed fixed-wing aerofoil measurements on the analysis and performance of flapping bird wings

Spedding, Geoff; Hedenström, Anders LU ; McArthur, John and Rosén, Mikael LU (2008) In Journal of Experimental Biology 211(2). p.215-223
Abstract
Bird flight occurs over a range of Reynolds numbers (Re; 104Re105, where Re is a measure of the relative importance of inertia and viscosity) that includes regimes where standard aerofoil performance is difficult to predict, compute or measure, with large performance jumps in response to small changes in geometry or environmental conditions. A comparison of measurements of fixed wing performance as a function of Re, combined with quantitative flow visualisation techniques, shows that, surprisingly, wakes of flapping bird wings at moderate flight speeds admit to certain simplifications where their basic properties can be understood through quasi-steady analysis. Indeed, a commonly cited measure of the relative flapping frequency, or wake... (More)
Bird flight occurs over a range of Reynolds numbers (Re; 104Re105, where Re is a measure of the relative importance of inertia and viscosity) that includes regimes where standard aerofoil performance is difficult to predict, compute or measure, with large performance jumps in response to small changes in geometry or environmental conditions. A comparison of measurements of fixed wing performance as a function of Re, combined with quantitative flow visualisation techniques, shows that, surprisingly, wakes of flapping bird wings at moderate flight speeds admit to certain simplifications where their basic properties can be understood through quasi-steady analysis. Indeed, a commonly cited measure of the relative flapping frequency, or wake unsteadiness, the Strouhal number, is seen to be approximately constant in accordance with a simple requirement for maintaining a moderate local angle of attack on the wing. Together, the measurements imply a fine control of boundary layer separation on the wings, with implications for control strategies and wing shape selection by natural and artificial fliers. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
animal flight, aerofoil, lift-drag polar, wake analysis, Reynolds number
in
Journal of Experimental Biology
volume
211
issue
2
pages
215 - 223
publisher
The Company of Biologists Ltd
external identifiers
  • wos:000253196300009
  • scopus:39049149132
ISSN
1477-9145
DOI
10.1242/jeb.007823
language
English
LU publication?
yes
id
6672abec-1150-4d4e-9735-ede0ffa885d9 (old id 954553)
date added to LUP
2008-01-25 12:42:39
date last changed
2017-07-02 03:38:04
@article{6672abec-1150-4d4e-9735-ede0ffa885d9,
  abstract     = {Bird flight occurs over a range of Reynolds numbers (Re; 104Re105, where Re is a measure of the relative importance of inertia and viscosity) that includes regimes where standard aerofoil performance is difficult to predict, compute or measure, with large performance jumps in response to small changes in geometry or environmental conditions. A comparison of measurements of fixed wing performance as a function of Re, combined with quantitative flow visualisation techniques, shows that, surprisingly, wakes of flapping bird wings at moderate flight speeds admit to certain simplifications where their basic properties can be understood through quasi-steady analysis. Indeed, a commonly cited measure of the relative flapping frequency, or wake unsteadiness, the Strouhal number, is seen to be approximately constant in accordance with a simple requirement for maintaining a moderate local angle of attack on the wing. Together, the measurements imply a fine control of boundary layer separation on the wings, with implications for control strategies and wing shape selection by natural and artificial fliers.},
  author       = {Spedding, Geoff and Hedenström, Anders and McArthur, John and Rosén, Mikael},
  issn         = {1477-9145},
  keyword      = {animal flight,aerofoil,lift-drag polar,wake analysis,Reynolds number},
  language     = {eng},
  number       = {2},
  pages        = {215--223},
  publisher    = {The Company of Biologists Ltd},
  series       = {Journal of Experimental Biology},
  title        = {The implications of low-speed fixed-wing aerofoil measurements on the analysis and performance of flapping bird wings},
  url          = {http://dx.doi.org/10.1242/jeb.007823},
  volume       = {211},
  year         = {2008},
}