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Aerodynamics of the hovering hummingbird
Douglas R Warrick1, Bret W Tobalske, Donald R Powers
1Department of Zoology, Oregon State University, 3029 Cordley Hall, Corvallis, Oregon 97331, USA. warrickd@science.oregonstate.edu
Nature
|June 24, 2005
Summary
Hummingbirds generate most of their hovering lift during the downstroke, unlike insects. This force asymmetry, driven by wing inversion, distinguishes avian flight despite similarities in vortex dynamics.
Area of Science:
- Biomechanics
- Aerodynamics
- Ornithology
Background:
- Hummingbirds (Trochilidae) are often assumed to use insect-like aerodynamic mechanisms for hovering.
- Kinematic symmetry in hummingbird wingbeats suggests equal lift generation during upstroke and downstroke.
- This assumption influences aerodynamic models and empirical studies of hummingbird flight.
Purpose of the Study:
- To investigate the force production asymmetry during hovering in hummingbirds.
- To compare hummingbird aerodynamic mechanisms with those of insects.
- To analyze the role of wing kinematics and morphology in hummingbird flight.
Main Methods:
- Digital particle image velocimetry (DPIV) was used to measure the wake of hovering rufous hummingbirds (Selasphorus rufus).
- Analysis focused on wake structure to infer aerodynamic forces.
- Wing kinematics and morphology were considered in relation to force generation.
Main Results:
- Hummingbirds exhibit significant force asymmetry, generating 75% of weight support during the downstroke and 25% during the upstroke.
- Wing inversion during the upstroke likely contributes to this force asymmetry.
- Leading-edge vortices observed during the downstroke suggest operation at low Reynolds numbers, similar to insects.
Conclusions:
- Hummingbird hovering is characterized by force asymmetry, contrasting with the assumed equal contribution from upstroke and downstroke.
- Despite similarities in vortex dynamics with insects, hummingbird flight is distinct due to avian body plan.
- The study highlights the unique aerodynamic strategies employed by hummingbirds.
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