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Published February 2014 | public
Journal Article

Bending rules for animal propulsion


Animal propulsors such as wings and fins bend during motion and these bending patterns are believed to contribute to the high efficiency of animal movements compared with those of man-made designs. However, efforts to implement flexible designs have been met with contradictory performance results. Consequently, there is no clear understanding of the role played by propulsor flexibility or, more fundamentally, how flexible propulsors should be designed for optimal performance. Here we demonstrate that during steady-state motion by a wide range of animals, from fruit flies to humpback whales, operating in either air or water, natural propulsors bend in similar ways within a highly predictable range of characteristic motions. By providing empirical design criteria derived from natural propulsors that have convergently arrived at a limited design space, these results provide a new framework from which to understand and design flexible propulsors.

Additional Information

© 2014 Macmillan Publishers Limited. Received 22 May 2013 | Accepted 22 Jan 2014 | Published 18 Feb 2014. This work was supported by an ONR MURI award to J.H.C. (N000140810654) and National Science Foundation Grant OCE 0623508 to J.H.C., S.P.C. and J.O.D. We thank C. Syslo and K. Kiefer for assistance with video collection and A. Shomberg for statistical advice. We also thank photographers for use of their images in Fig. 1: (a) E. Schipul (http://www.flickr.com/photos/eschipul), (b) M. Baird (Michael L. Baird, flickr. bairdphotos.com), (d) J. Fabrice, (fabrice@marinemegafauna.org), (e) D. Wrobel, (http://www.wrobelphoto.com), (f) E. Van 3000 from in Flanders fields—Belgiquistan—United Tribes of Europe (CC-BY-SA-2.0). We also thank photographers for use of their images in Fig. 5: G. Humes, The US Fish and Wildlife Service, B. Nyman, B. Weinstein, OpenCage and E. Van 3000.

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