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How swifts control their glide performance with morphing wings

Lentink, D; Muller, U K; Stamhuis, E J; de Kat, R; van Gestel, W; Veldhuis, L L M; Henningsson, Per LU ; Hedenström, Anders LU ; Videler, J J and van Leeuwen, J L (2007) In Nature 446(7139). p.1082-1085
Abstract
Gliding birds continually change the shape and size of their wings(1-6), presumably to exploit the profound effect of wing morphology on aerodynamic performance(7-9). That birds should adjust wing sweep to suit glide speed has been predicted qualitatively by analytical glide models(2,10), which extrapolated the wing's performance envelope from aerodynamic theory. Here we describe the aerodynamic and structural performance of actual swift wings, as measured in a wind tunnel, and on this basis build a semiempirical glide model. By measuring inside and outside swifts' behavioural envelope, we show that choosing the most suitable sweep can halve sink speed or triple turning rate. Extended wings are superior for slow glides and turns; swept... (More)
Gliding birds continually change the shape and size of their wings(1-6), presumably to exploit the profound effect of wing morphology on aerodynamic performance(7-9). That birds should adjust wing sweep to suit glide speed has been predicted qualitatively by analytical glide models(2,10), which extrapolated the wing's performance envelope from aerodynamic theory. Here we describe the aerodynamic and structural performance of actual swift wings, as measured in a wind tunnel, and on this basis build a semiempirical glide model. By measuring inside and outside swifts' behavioural envelope, we show that choosing the most suitable sweep can halve sink speed or triple turning rate. Extended wings are superior for slow glides and turns; swept wings are superior for fast glides and turns. This superiority is due to better aerodynamic performance - with the exception of fast turns. Swept wings are less effective at generating lift while turning at high speeds, but can bear the extreme loads. Finally, our glide model predicts that cost-effective gliding occurs at speeds of 8 - 10 m s(-1), whereas agility-related figures of merit peak at 15 - 25 m s(-1). In fact, swifts spend the night ('roost') in flight at 8 - 10 m s(-1) ( ref. 11), thus our model can explain this choice for a resting behaviour(11,12). Morphing not only adjusts birds' wing performance to the task at hand, but could also control the flight of future aircraft(7). (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Nature
volume
446
issue
7139
pages
1082 - 1085
publisher
Nature Publishing Group
external identifiers
  • wos:000245950400050
  • scopus:34247630555
ISSN
0028-0836
DOI
10.1038/nature05733
language
English
LU publication?
yes
id
41714ec8-2136-48c0-b175-c71b150972e4 (old id 168570)
date added to LUP
2007-07-03 13:38:23
date last changed
2017-10-01 03:38:36
@article{41714ec8-2136-48c0-b175-c71b150972e4,
  abstract     = {Gliding birds continually change the shape and size of their wings(1-6), presumably to exploit the profound effect of wing morphology on aerodynamic performance(7-9). That birds should adjust wing sweep to suit glide speed has been predicted qualitatively by analytical glide models(2,10), which extrapolated the wing's performance envelope from aerodynamic theory. Here we describe the aerodynamic and structural performance of actual swift wings, as measured in a wind tunnel, and on this basis build a semiempirical glide model. By measuring inside and outside swifts' behavioural envelope, we show that choosing the most suitable sweep can halve sink speed or triple turning rate. Extended wings are superior for slow glides and turns; swept wings are superior for fast glides and turns. This superiority is due to better aerodynamic performance - with the exception of fast turns. Swept wings are less effective at generating lift while turning at high speeds, but can bear the extreme loads. Finally, our glide model predicts that cost-effective gliding occurs at speeds of 8 - 10 m s(-1), whereas agility-related figures of merit peak at 15 - 25 m s(-1). In fact, swifts spend the night ('roost') in flight at 8 - 10 m s(-1) ( ref. 11), thus our model can explain this choice for a resting behaviour(11,12). Morphing not only adjusts birds' wing performance to the task at hand, but could also control the flight of future aircraft(7).},
  author       = {Lentink, D and Muller, U K and Stamhuis, E J and de Kat, R and van Gestel, W and Veldhuis, L L M and Henningsson, Per and Hedenström, Anders and Videler, J J and van Leeuwen, J L},
  issn         = {0028-0836},
  language     = {eng},
  number       = {7139},
  pages        = {1082--1085},
  publisher    = {Nature Publishing Group},
  series       = {Nature},
  title        = {How swifts control their glide performance with morphing wings},
  url          = {http://dx.doi.org/10.1038/nature05733},
  volume       = {446},
  year         = {2007},
}