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Field estimates of body drag coefficient on the basis of dives in passerine birds

Hedenström, Anders LU and Liechti, F (2001) In Journal of Experimental Biology 204(6). p.1167-1175
Abstract
During forward flight, a bird's body generates drag that tends to decelerate its speed. By flapping its wings, or by converting potential energy into work if gliding, the bird produces both lift and thrust to balance the pull of gravity and drag. In flight mechanics, a dimensionless number, the body drag coefficient (C-D,C-par), describes the magnitude of the drag caused by the body. The drag coefficient depends on the shape (or streamlining), the surface texture of the body and the Reynolds number. It is an important variable when using flight mechanical models to estimate the potential migratory flight range and characteristic flight speeds of birds, Previous wind tunnel measurements on dead, frozen bird bodies indicated that C(D,pa)r is... (More)
During forward flight, a bird's body generates drag that tends to decelerate its speed. By flapping its wings, or by converting potential energy into work if gliding, the bird produces both lift and thrust to balance the pull of gravity and drag. In flight mechanics, a dimensionless number, the body drag coefficient (C-D,C-par), describes the magnitude of the drag caused by the body. The drag coefficient depends on the shape (or streamlining), the surface texture of the body and the Reynolds number. It is an important variable when using flight mechanical models to estimate the potential migratory flight range and characteristic flight speeds of birds, Previous wind tunnel measurements on dead, frozen bird bodies indicated that C(D,pa)r is 0.4 for small birds, while large birds should have lower values of approximately 0.2. More recent studies of a few birds flying in a wind tunnel suggested that previous values probably overestimated C-D,C-par. We measured maximum dive speeds of passerine birds during the spring migration across the western Mediterranean. When the birds reach their top speed, the pull of gravity should balance the drag of the body land wings), giving us an opportunity to estimate C-D,C-par. Our results indicate that C-D,C-par decreases with increasing Reynolds number within the range 0.17-0.77, with a mean C-D,C-par of 0.37 for small passerines, A somewhat lower mean value could not be excluded because diving birds may control their speed below the theoretical maximum, Our measurements therefore support the notion that 0.4 (the 'old' default value) is a realistic value of C-D,C-par for Small passerines. (Less)
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author
organization
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Contribution to journal
publication status
published
subject
in
Journal of Experimental Biology
volume
204
issue
6
pages
1167 - 1175
publisher
The Company of Biologists Ltd
external identifiers
  • scopus:0035745360
ISSN
1477-9145
language
English
LU publication?
yes
id
cc103c3e-7256-43f3-ac62-37099b390767 (old id 145829)
alternative location
http://jeb.biologists.org/cgi/content/abstract/204/6/1167
date added to LUP
2007-06-26 07:57:39
date last changed
2018-02-04 03:34:28
@article{cc103c3e-7256-43f3-ac62-37099b390767,
  abstract     = {During forward flight, a bird's body generates drag that tends to decelerate its speed. By flapping its wings, or by converting potential energy into work if gliding, the bird produces both lift and thrust to balance the pull of gravity and drag. In flight mechanics, a dimensionless number, the body drag coefficient (C-D,C-par), describes the magnitude of the drag caused by the body. The drag coefficient depends on the shape (or streamlining), the surface texture of the body and the Reynolds number. It is an important variable when using flight mechanical models to estimate the potential migratory flight range and characteristic flight speeds of birds, Previous wind tunnel measurements on dead, frozen bird bodies indicated that C(D,pa)r is 0.4 for small birds, while large birds should have lower values of approximately 0.2. More recent studies of a few birds flying in a wind tunnel suggested that previous values probably overestimated C-D,C-par. We measured maximum dive speeds of passerine birds during the spring migration across the western Mediterranean. When the birds reach their top speed, the pull of gravity should balance the drag of the body land wings), giving us an opportunity to estimate C-D,C-par. Our results indicate that C-D,C-par decreases with increasing Reynolds number within the range 0.17-0.77, with a mean C-D,C-par of 0.37 for small passerines, A somewhat lower mean value could not be excluded because diving birds may control their speed below the theoretical maximum, Our measurements therefore support the notion that 0.4 (the 'old' default value) is a realistic value of C-D,C-par for Small passerines.},
  author       = {Hedenström, Anders and Liechti, F},
  issn         = {1477-9145},
  language     = {eng},
  number       = {6},
  pages        = {1167--1175},
  publisher    = {The Company of Biologists Ltd},
  series       = {Journal of Experimental Biology},
  title        = {Field estimates of body drag coefficient on the basis of dives in passerine birds},
  volume       = {204},
  year         = {2001},
}