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Hovering performance of Anna's hummingbirds (Calypte anna) in ground effect

Kim, Erica J.; Wolf, Marta LU ; Ortega-Jimenez, Victor Manuel; Cheng, Stanley H. and Dudley, Robert (2014) In Journal of the Royal Society Interface 11(98).
Abstract
Aerodynamic performance and energetic savings for flight in ground effect are theoretically maximized during hovering, but have never been directly measured for flying animals. We evaluated flight kinematics, metabolic rates and induced flow velocities for Anna's hummingbirds hovering at heights (relative to wing length R 5.5 cm) of 0.7R, 0.9R, 1.1R, 1.7R, 2.2R and 8R above a solid surface. Flight at heights less than or equal to 1.1R resulted in significant reductions in the body angle, tail angle, anatomical stroke plane angle, wake-induced velocity, and mechanical and metabolic power expenditures when compared with flight at the control height of 8R. By contrast, stroke plane angle relative to horizontal, wingbeat amplitude and wingbeat... (More)
Aerodynamic performance and energetic savings for flight in ground effect are theoretically maximized during hovering, but have never been directly measured for flying animals. We evaluated flight kinematics, metabolic rates and induced flow velocities for Anna's hummingbirds hovering at heights (relative to wing length R 5.5 cm) of 0.7R, 0.9R, 1.1R, 1.7R, 2.2R and 8R above a solid surface. Flight at heights less than or equal to 1.1R resulted in significant reductions in the body angle, tail angle, anatomical stroke plane angle, wake-induced velocity, and mechanical and metabolic power expenditures when compared with flight at the control height of 8R. By contrast, stroke plane angle relative to horizontal, wingbeat amplitude and wingbeat frequency were unexpectedly independent of height from ground. Qualitative smoke visualizations suggest that each wing generates a vortex ring during both down-and upstroke. These rings expand upon reaching the ground and present a complex turbulent interaction below the bird's body. Nonetheless, hovering near surfaces results in substantial energetic benefits for hummingbirds, and by inference for all volant taxa that either feed at flowers or otherwise fly close to plant or other surfaces. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
ground effect, hovering, induced velocity, metabolic power, vortex wake
in
Journal of the Royal Society Interface
volume
11
issue
98
publisher
Royal Society
external identifiers
  • pmid:24990291
  • wos:000338519300014
  • scopus:84905053621
ISSN
1742-5662
DOI
10.1098/rsif.2014.0505
language
English
LU publication?
yes
id
c7ad00ee-77ea-4ca0-a297-53d96fb11653 (old id 4602578)
date added to LUP
2014-09-04 09:46:50
date last changed
2017-10-22 03:15:17
@article{c7ad00ee-77ea-4ca0-a297-53d96fb11653,
  abstract     = {Aerodynamic performance and energetic savings for flight in ground effect are theoretically maximized during hovering, but have never been directly measured for flying animals. We evaluated flight kinematics, metabolic rates and induced flow velocities for Anna's hummingbirds hovering at heights (relative to wing length R 5.5 cm) of 0.7R, 0.9R, 1.1R, 1.7R, 2.2R and 8R above a solid surface. Flight at heights less than or equal to 1.1R resulted in significant reductions in the body angle, tail angle, anatomical stroke plane angle, wake-induced velocity, and mechanical and metabolic power expenditures when compared with flight at the control height of 8R. By contrast, stroke plane angle relative to horizontal, wingbeat amplitude and wingbeat frequency were unexpectedly independent of height from ground. Qualitative smoke visualizations suggest that each wing generates a vortex ring during both down-and upstroke. These rings expand upon reaching the ground and present a complex turbulent interaction below the bird's body. Nonetheless, hovering near surfaces results in substantial energetic benefits for hummingbirds, and by inference for all volant taxa that either feed at flowers or otherwise fly close to plant or other surfaces.},
  articleno    = {20140505},
  author       = {Kim, Erica J. and Wolf, Marta and Ortega-Jimenez, Victor Manuel and Cheng, Stanley H. and Dudley, Robert},
  issn         = {1742-5662},
  keyword      = {ground effect,hovering,induced velocity,metabolic power,vortex wake},
  language     = {eng},
  number       = {98},
  publisher    = {Royal Society},
  series       = {Journal of the Royal Society Interface},
  title        = {Hovering performance of Anna's hummingbirds (Calypte anna) in ground effect},
  url          = {http://dx.doi.org/10.1098/rsif.2014.0505},
  volume       = {11},
  year         = {2014},
}