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Leading edge vortex in a slow-flying passerine.

Muijres, Florian LU ; Johansson, Christoffer LU and Hedenström, Anders LU (2012) In Biology Letters 8(4). p.554-557
Abstract
Most hovering animals, such as insects and hummingbirds, enhance lift by producing leading edge vortices (LEVs) and by using both the downstroke and upstroke for lift production. By contrast, most hovering passerine birds primarily use the downstroke to generate lift. To compensate for the nearly inactive upstroke, weight support during the downstroke needs to be relatively higher in passerines when compared with, e.g. hummingbirds. Here we show, by capturing the airflow around the wing of a freely flying pied flycatcher, that passerines may use LEVs during the downstroke to increase lift. The LEV contributes up to 49 per cent to weight support, which is three times higher than in hummingbirds, suggesting that avian hoverers compensate for... (More)
Most hovering animals, such as insects and hummingbirds, enhance lift by producing leading edge vortices (LEVs) and by using both the downstroke and upstroke for lift production. By contrast, most hovering passerine birds primarily use the downstroke to generate lift. To compensate for the nearly inactive upstroke, weight support during the downstroke needs to be relatively higher in passerines when compared with, e.g. hummingbirds. Here we show, by capturing the airflow around the wing of a freely flying pied flycatcher, that passerines may use LEVs during the downstroke to increase lift. The LEV contributes up to 49 per cent to weight support, which is three times higher than in hummingbirds, suggesting that avian hoverers compensate for the nearly inactive upstroke by generating stronger LEVs. Contrary to other animals, the LEV strength in the flycatcher is lowest near the wing tip, instead of highest. This is correlated with a spanwise reduction of the wing's angle-of-attack, partly owing to upward bending of primary feathers. We suggest that this helps to delay bursting and shedding of the particularly strong LEV in passerines. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
bird flight, leading edge vortex, aerodynamics, aeroelastics, pied flycatcher, wind tunnel
in
Biology Letters
volume
8
issue
4
pages
554 - 557
publisher
Royal Society
external identifiers
  • wos:000306361700022
  • pmid:22417792
  • scopus:84864490098
ISSN
1744-9561
DOI
10.1098/rsbl.2012.0130
project
CAnMove
language
English
LU publication?
yes
id
45b1a024-8776-45d0-aca5-c2dfd2c228d9 (old id 2431830)
date added to LUP
2012-05-08 10:33:01
date last changed
2017-10-08 03:15:42
@article{45b1a024-8776-45d0-aca5-c2dfd2c228d9,
  abstract     = {Most hovering animals, such as insects and hummingbirds, enhance lift by producing leading edge vortices (LEVs) and by using both the downstroke and upstroke for lift production. By contrast, most hovering passerine birds primarily use the downstroke to generate lift. To compensate for the nearly inactive upstroke, weight support during the downstroke needs to be relatively higher in passerines when compared with, e.g. hummingbirds. Here we show, by capturing the airflow around the wing of a freely flying pied flycatcher, that passerines may use LEVs during the downstroke to increase lift. The LEV contributes up to 49 per cent to weight support, which is three times higher than in hummingbirds, suggesting that avian hoverers compensate for the nearly inactive upstroke by generating stronger LEVs. Contrary to other animals, the LEV strength in the flycatcher is lowest near the wing tip, instead of highest. This is correlated with a spanwise reduction of the wing's angle-of-attack, partly owing to upward bending of primary feathers. We suggest that this helps to delay bursting and shedding of the particularly strong LEV in passerines.},
  author       = {Muijres, Florian and Johansson, Christoffer and Hedenström, Anders},
  issn         = {1744-9561},
  keyword      = {bird flight,leading edge vortex,aerodynamics,aeroelastics,pied flycatcher,wind tunnel},
  language     = {eng},
  number       = {4},
  pages        = {554--557},
  publisher    = {Royal Society},
  series       = {Biology Letters},
  title        = {Leading edge vortex in a slow-flying passerine.},
  url          = {http://dx.doi.org/10.1098/rsbl.2012.0130},
  volume       = {8},
  year         = {2012},
}