Mechanical power curve measured in the wake of pied flycatchers indicates modulation of parasite power across flight speeds
(2018) In Journal of the Royal Society Interface 15(138).- Abstract
How aerodynamic power required for animal flight varies with flight speed determines optimal speeds during foraging and migratory flight. Despite its relevance, aerodynamic power provides an elusive quantity to measure directly in animal flight. Here, we determine the aerodynamic power from wake velocity fields, measured using tomographical particle image velocimetry, of pied flycatchers flying freely in a wind tunnel. We find a shallow U-shaped power curve, which is flatter than expected by theory. Based on how the birds vary body angle with speed, we speculate that the shallow curve results from increased body drag coefficient and body frontal area at lower flight speeds. Including modulation of body drag in the model results in a... (More)
How aerodynamic power required for animal flight varies with flight speed determines optimal speeds during foraging and migratory flight. Despite its relevance, aerodynamic power provides an elusive quantity to measure directly in animal flight. Here, we determine the aerodynamic power from wake velocity fields, measured using tomographical particle image velocimetry, of pied flycatchers flying freely in a wind tunnel. We find a shallow U-shaped power curve, which is flatter than expected by theory. Based on how the birds vary body angle with speed, we speculate that the shallow curve results from increased body drag coefficient and body frontal area at lower flight speeds. Including modulation of body drag in the model results in a more reasonable fit with data than the traditional model. From the wake structure, we also find a single starting vortex generated from the two wings during the downstroke across flight speeds (1–9 m s21). This is accomplished by the arm wings interacting at the beginning of the downstroke, generating a unified starting vortex above the body of the bird. We interpret this as a mechanism resulting in a rather uniform downwash and low induced power, which can help explain the higher aerodynamic performance in birds compared with bats.
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- author
- Christoffer Johansson, L. LU ; Maeda, Masateru LU ; Henningsson, Per LU and Hedenström, Anders LU
- organization
- publishing date
- 2018-01-01
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Animal flight, Bird aerodynamics, Flapping flight power curve, Tomographic particle image velocimetry, Wake energy
- in
- Journal of the Royal Society Interface
- volume
- 15
- issue
- 138
- article number
- 20170814
- publisher
- The Royal Society of Canada
- external identifiers
-
- pmid:29386402
- scopus:85048554375
- ISSN
- 1742-5689
- DOI
- 10.1098/rsif.2017.0814
- language
- English
- LU publication?
- yes
- id
- cfc50708-acb3-4e39-9c8b-ec6679346e70
- date added to LUP
- 2018-07-03 11:09:09
- date last changed
- 2024-05-27 13:47:40
@article{cfc50708-acb3-4e39-9c8b-ec6679346e70,
abstract = {{<p>How aerodynamic power required for animal flight varies with flight speed determines optimal speeds during foraging and migratory flight. Despite its relevance, aerodynamic power provides an elusive quantity to measure directly in animal flight. Here, we determine the aerodynamic power from wake velocity fields, measured using tomographical particle image velocimetry, of pied flycatchers flying freely in a wind tunnel. We find a shallow U-shaped power curve, which is flatter than expected by theory. Based on how the birds vary body angle with speed, we speculate that the shallow curve results from increased body drag coefficient and body frontal area at lower flight speeds. Including modulation of body drag in the model results in a more reasonable fit with data than the traditional model. From the wake structure, we also find a single starting vortex generated from the two wings during the downstroke across flight speeds (1–9 m s<sup>21</sup>). This is accomplished by the arm wings interacting at the beginning of the downstroke, generating a unified starting vortex above the body of the bird. We interpret this as a mechanism resulting in a rather uniform downwash and low induced power, which can help explain the higher aerodynamic performance in birds compared with bats.</p>}},
author = {{Christoffer Johansson, L. and Maeda, Masateru and Henningsson, Per and Hedenström, Anders}},
issn = {{1742-5689}},
keywords = {{Animal flight; Bird aerodynamics; Flapping flight power curve; Tomographic particle image velocimetry; Wake energy}},
language = {{eng}},
month = {{01}},
number = {{138}},
publisher = {{The Royal Society of Canada}},
series = {{Journal of the Royal Society Interface}},
title = {{Mechanical power curve measured in the wake of pied flycatchers indicates modulation of parasite power across flight speeds}},
url = {{http://dx.doi.org/10.1098/rsif.2017.0814}},
doi = {{10.1098/rsif.2017.0814}},
volume = {{15}},
year = {{2018}},
}