Efficiency of lift production in flapping and gliding flight of swifts.

Many flying animals use both flapping and gliding flight as part of their routine behaviour. These two kinematic patterns impose conflicting requirements on wing design for aerodynamic efficiency and, in the absence of extreme morphing, wings cannot be optimised for both flight modes. In gliding fli...

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Autores principales:	Per Henningsson, Anders Hedenström, Richard J Bomphrey
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2014
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/6deca58ae5ad4863affde56681afc35b
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spelling	oai:doaj.org-article:6deca58ae5ad4863affde56681afc35b2021-11-18T08:30:23ZEfficiency of lift production in flapping and gliding flight of swifts.1932-620310.1371/journal.pone.0090170https://doaj.org/article/6deca58ae5ad4863affde56681afc35b2014-01-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/24587260/?tool=EBIhttps://doaj.org/toc/1932-6203Many flying animals use both flapping and gliding flight as part of their routine behaviour. These two kinematic patterns impose conflicting requirements on wing design for aerodynamic efficiency and, in the absence of extreme morphing, wings cannot be optimised for both flight modes. In gliding flight, the wing experiences uniform incident flow and the optimal shape is a high aspect ratio wing with an elliptical planform. In flapping flight, on the other hand, the wing tip travels faster than the root, creating a spanwise velocity gradient. To compensate, the optimal wing shape should taper towards the tip (reducing the local chord) and/or twist from root to tip (reducing local angle of attack). We hypothesised that, if a bird is limited in its ability to morph its wings and adapt its wing shape to suit both flight modes, then a preference towards flapping flight optimization will be expected since this is the most energetically demanding flight mode. We tested this by studying a well-known flap-gliding species, the common swift, by measuring the wakes generated by two birds, one in gliding and one in flapping flight in a wind tunnel. We calculated span efficiency, the efficiency of lift production, and found that the flapping swift had consistently higher span efficiency than the gliding swift. This supports our hypothesis and suggests that even though swifts have been shown previously to increase their lift-to-drag ratio substantially when gliding, the wing morphology is tuned to be more aerodynamically efficient in generating lift during flapping. Since body drag can be assumed to be similar for both flapping and gliding, it follows that the higher total drag in flapping flight compared with gliding flight is primarily a consequence of an increase in wing profile drag due to the flapping motion, exceeding the reduction in induced drag.Per HenningssonAnders HedenströmRichard J BomphreyPublic Library of Science (PLoS)articleMedicineRScienceQENPLoS ONE, Vol 9, Iss 2, p e90170 (2014)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Per Henningsson Anders Hedenström Richard J Bomphrey Efficiency of lift production in flapping and gliding flight of swifts.
description	Many flying animals use both flapping and gliding flight as part of their routine behaviour. These two kinematic patterns impose conflicting requirements on wing design for aerodynamic efficiency and, in the absence of extreme morphing, wings cannot be optimised for both flight modes. In gliding flight, the wing experiences uniform incident flow and the optimal shape is a high aspect ratio wing with an elliptical planform. In flapping flight, on the other hand, the wing tip travels faster than the root, creating a spanwise velocity gradient. To compensate, the optimal wing shape should taper towards the tip (reducing the local chord) and/or twist from root to tip (reducing local angle of attack). We hypothesised that, if a bird is limited in its ability to morph its wings and adapt its wing shape to suit both flight modes, then a preference towards flapping flight optimization will be expected since this is the most energetically demanding flight mode. We tested this by studying a well-known flap-gliding species, the common swift, by measuring the wakes generated by two birds, one in gliding and one in flapping flight in a wind tunnel. We calculated span efficiency, the efficiency of lift production, and found that the flapping swift had consistently higher span efficiency than the gliding swift. This supports our hypothesis and suggests that even though swifts have been shown previously to increase their lift-to-drag ratio substantially when gliding, the wing morphology is tuned to be more aerodynamically efficient in generating lift during flapping. Since body drag can be assumed to be similar for both flapping and gliding, it follows that the higher total drag in flapping flight compared with gliding flight is primarily a consequence of an increase in wing profile drag due to the flapping motion, exceeding the reduction in induced drag.
format	article
author	Per Henningsson Anders Hedenström Richard J Bomphrey
author_facet	Per Henningsson Anders Hedenström Richard J Bomphrey
author_sort	Per Henningsson
title	Efficiency of lift production in flapping and gliding flight of swifts.
title_short	Efficiency of lift production in flapping and gliding flight of swifts.
title_full	Efficiency of lift production in flapping and gliding flight of swifts.
title_fullStr	Efficiency of lift production in flapping and gliding flight of swifts.
title_full_unstemmed	Efficiency of lift production in flapping and gliding flight of swifts.
title_sort	efficiency of lift production in flapping and gliding flight of swifts.
publisher	Public Library of Science (PLoS)
publishDate	2014
url	https://doaj.org/article/6deca58ae5ad4863affde56681afc35b
work_keys_str_mv	AT perhenningsson efficiencyofliftproductioninflappingandglidingflightofswifts AT andershedenstrom efficiencyofliftproductioninflappingandglidingflightofswifts AT richardjbomphrey efficiencyofliftproductioninflappingandglidingflightofswifts
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Efficiency of lift production in flapping and gliding flight of swifts.

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