Aerodynamic forces of revolving hummingbird wings and wing models

Authors

  • Douglas L. Altshuler,

    Corresponding author
    1. Section of Integrative Biology, University of Texas at Austin, Austin, Texas, 78712, U.S.A.
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  • Robert Dudley,

    1. Section of Integrative Biology, University of Texas at Austin, Austin, Texas, 78712, U.S.A.
    2. Smithsonian Tropical Research Institute, P.O. Box 2072, Balboa, Republic of Panama
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    • 3

      Department of Integrative Biology, University of California, Berkeley, CA 94720, U.S.A.

  • Charles P. Ellington

    1. Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, U.K.
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* All correspondence to present address: D. L. Altshuler, California Institute of Technology, Mail Code 138–78, 1200 East California Boulevard, Pasadena, CA 91125, U.S.A. E-mail: doug@caltech.edu

Abstract

A central challenge to the study of animal aerodynamics has been the measurement of forces generated by flapping wings. Relative to wings of other birds, hummingbird wings are of particular interest in that the smaller species operate in more viscous regimes (5000 < Re < 10 000) for which substantial drag and reduced lift:drag coefficients might be expected. Lift and drag forces were measured on mounted hummingbird wings and wing models spinning in continuous tipwise revolution about the wing base. Lift coefficients tended to increase as wing models became more realistic (i.e. with sharpened leading edges and with substantial camber). Lift:drag ratios of real wings were substantially higher than those of wing models, suggesting morphological contributions of feathers to lift enhancement and drag reduction. At Re= 5000, high values of the lift:drag ratio (8–16) at low angles of attack suggest that wings of hummingbirds are exceptionally good at producing lift.

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