Strouhal number for flying and swimming in rhinoceros auklets Cerorhinca monocerata
Alcids propel themselves by flapping wings in air and water that have vastly different densities. We hypothesized that alcids change wing kinematics and maintain Strouhal numbers (St = fA/U, where f is wingbeat frequency, A is the wingbeat amplitude, and U is forward speed) within a certain range, t...
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Published in | Journal of avian biology Vol. 46; no. 4; pp. 406 - 411 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
Oxford, UK
Blackwell Publishing Ltd
01.07.2015
Nordic Society Oikos John Wiley & Sons, Inc |
Subjects | |
Online Access | Get full text |
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Summary: | Alcids propel themselves by flapping wings in air and water that have vastly different densities. We hypothesized that alcids change wing kinematics and maintain Strouhal numbers (St = fA/U, where f is wingbeat frequency, A is the wingbeat amplitude, and U is forward speed) within a certain range, to achieve efficient locomotion during both flying and swimming. We used acceleration and GPS loggers to measure the wingbeat frequency and forward speed of free‐ranging rhinoceros auklets Cerorhinca monocerata during both flying and swimming. We also measured wingbeat amplitude from video footage taken in the wild. On average, wingbeat frequency, forward speed, and wingbeat amplitude were 8.9 Hz, 15.3 m s⁻¹, and 0.39 m, respectively, during flying, and 2.6 Hz, 1.3 m s⁻¹, and 0.18 m, respectively, during swimming. The smaller wingbeat amplitude during swimming was achieved by partially folding the wings, while maintaining the dorso‐ventral wingbeat angle. Mean St was 0.23 during flying and 0.36 during swimming. The higher St value for swimming might be related to the higher thrust force required for propulsion in water. Our results suggest that rhinoceros auklets maintain St for both flying and swimming within the range (0.2–0.4) that propulsive efficiency is known to be high and St in both flying specialists and swimming specialists are known to converge. |
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Bibliography: | http://dx.doi.org/10.1111/jav.00642 ark:/67375/WNG-837Z3H4G-V istex:4714EA279C2E14D34DC9221D9708F9B5475C11C9 ArticleID:JAV642 JSPS Grant-in-Aid for Scientific Research - No. 20241001 JSPS Research Fellowship for Young Scientists - No. 26-5363 |
ISSN: | 0908-8857 1600-048X |
DOI: | 10.1111/jav.00642 |