Leading-edge vortex lifts swifts
- PMID: 15591209
- DOI: 10.1126/science.1104682
Leading-edge vortex lifts swifts
Abstract
The current understanding of how birds fly must be revised, because birds use their hand-wings in an unconventional way to generate lift and drag. Physical models of a common swift wing in gliding posture with a 60 degrees sweep of the sharp hand-wing leading edge were tested in a water tunnel. Interactions with the flow were measured quantitatively with digital particle image velocimetry at Reynolds numbers realistic for the gliding flight of a swift between 3750 and 37,500. The results show that gliding swifts can generate stable leading-edge vortices at small (5 degrees to 10 degrees) angles of attack. We suggest that the flow around the arm-wings of most birds can remain conventionally attached, whereas the swept-back hand-wings generate lift with leading-edge vortices.
Comment in
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Physiology. Turning on a dime.Science. 2004 Dec 10;306(5703):1899-900. doi: 10.1126/science.1107070. Science. 2004. PMID: 15591191 No abstract available.
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