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Structure of the vortex wake in hovering Anna's hummingbirds (Calypte anna).
- Source :
-
Proceedings of the Royal Society B: Biological Sciences . 12/22/2013, Vol. 280 Issue 1773, p1-7. 7p. - Publication Year :
- 2013
-
Abstract
- Hummingbirds are specialized hoverers for which the vortex wake has been described as a series of single vortex rings shed primarily during the downstroke. Recent findings in bats and birds, as well as in a recent study on Anna�s hummingbirds, suggest that each wing may shed a discrete vortex ring, yielding a bilaterally paired wake. Here, we describe the presence of two discrete rings in the wake of hovering Anna�s hummingbirds, and also infer force production through a wingbeat with contributions to weight support. Using flow visualization, we found separate vortices at the tip and root of each wing, with 15% stronger circulation at the wingtip than at the root during the downstroke. The upstroke wake is more complex, with near-continuous shedding of vorticity, and circulation of approximately equal magnitude at tip and root. Force estimates suggest that the downstroke contributes 66% of required weight support, whereas the upstroke generates 35%. We also identified a secondary vortex structure yielding 8�26% of weight support. Lift production in Anna�s hummingbirds is more evenly distributed between the stroke phases than previously estimated for Rufous hummingbirds, in accordance with the generally symmetric down- and upstrokes that characterize hovering in these birds. [ABSTRACT FROM AUTHOR]
- Subjects :
- *ANNA hummingbird
*WINGS (Anatomy)
*AVIAN anatomy
*VORTEX motion
*AERODYNAMICS
Subjects
Details
- Language :
- English
- ISSN :
- 09628452
- Volume :
- 280
- Issue :
- 1773
- Database :
- Academic Search Index
- Journal :
- Proceedings of the Royal Society B: Biological Sciences
- Publication Type :
- Academic Journal
- Accession number :
- 108281805
- Full Text :
- https://doi.org/10.1098/rspb.2013.2391