An unconventional mechanism of lift production during the downstroke in a hovering bird (<Emphasis Type="Italic">Zosterops japonicus</Emphasis>) |
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Authors: | Yu-Hung?Chang Shang-Chieh?Ting Chieh-Cheng?Liu Email author" target="_blank">Jing-Tang?YangEmail author Chyi-Yeou?Soong |
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Institution: | (1) Department of Mechanical Engineering, National Taiwan University, Taipei, 10617, Taiwan;(2) Department of Aerospace and Systems Engineering, Feng Chia University, Taichung, 40724, Taiwan; |
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Abstract: | An unconventional mechanism of ventral clap is exploited by hovering passerines to produce lift. Quantitative visualization
of the wake flow, analysis of kinematics and evaluation of the transient lift force was conducted to dissect the biomechanical
role of the ventral clap in the asymmetrical hovering flight of passerines. The ventral clap can first abate and then augment
lift production during the downstroke; the net effect of the ventral clap on lift production is, however, positive because
the extent of lift augmentation is greater than the extent of lift abatement. Moreover, the ventral clap is inferred to compensate
for the zero lift production of the upstroke because the clapping wings induce a substantial elevation of the lift force at
the end of the downstroke. Overall, our observations shed light on the aerodynamic function of the ventral clap and offer
biomechanical insight into how a bird hovers without kinematically mimicking hovering hummingbirds. |
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