The diverse hummingbird family (Trochilidae) has unique adaptations for nectarivory, among which is the ability to sustain hover-feeding. As hummingbirds mainly feed while hovering, it is crucial to maintain this ability throughout the annual cycle—especially during flight-feather moult, in which wing area is reduced. To quantify the aerodynamic characteristics and flow mechanisms of a hummingbird wing throughout the annual cycle, time-accurate aerodynamic loads and flow field measurements were correlated over a dynamically scaled wing model of Anna’s hummingbird (Calypte anna). We present measurements recorded over a model of a complete wing to evaluate the baseline aerodynamic characteristics and flow mechanisms. We found that the vorticity concentration that had developed from the wing’s leading-edge differs from the attached vorticity structure that was typically found over insects’ wings; firstly, it is more elongated along the wing chord, and secondly, it encounters high levels of fluctuations rather than a steady vortex. Lift characteristics resemble those of insects; however, a 20% increase in the lift-to-torque ratio was obtained for the hummingbird wing model. Time-accurate aerodynamic loads were also used to evaluate the time-evolution of the specific power required from the flight muscles, and the overall wingbeat power requirements nicely matched previous studies.
Bibliographical noteFunding Information:
Authors’ contributions. Y.A, Y.E. and N.S. designed the experiments and wrote the paper. Y.A. and Y.E. performed data gathering and analysis. Competing interests. We declare we have no competing interests. Funding. We received no funding for this study. Acknowledgements. We thank ATS, Applied Technologic Services, LTD (Herzelia, Israel) for providing the PIV system. We also thank Ms Dorin Avsaid, Mr Noam Neeman and Mr Roei Elfassy for their help obtaining the PIV data. We acknowledge Distinguished Professor Emeritus Daniel Weihs for his insightful remarks.
© 2017 The Authors.
- Animal flight
- Leading-edge vortex
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