QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online January 31, 2007
Journal of Experimental Biology 210, 685-698 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02692

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Peng, J. Articles by Lauder, G. V. Search for Related Content PubMed PubMed Citation Articles by Peng, J. Articles by Lauder, G. V. Social Bookmarking                         What's this?

Non-invasive measurement of instantaneous forces during aquatic locomotion: a case study of the bluegill sunfish pectoral fin

Jifeng Peng¹, John O. Dabiri^1,2,*, Peter G. Madden³ and George V. Lauder³

¹ Bioengineering, California Institute of Technology, Pasadena, CA 91125, USA
² Graduate Aeronautical Laboratories, California Institute of Technology, Pasadena, CA 91125, USA
³ Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA

^* Author for correspondence (e-mail: jodabiri{at}caltech.edu)

Accepted 12 December 2006

Swimming and flying animals generate unsteady locomotive forces by delivering net momentum into the fluid wake. Hence, swimming and flying forces can be quantified by measuring the momentum of animal wakes. A recently developed model provides an approach to empirically deduce swimming and flying forces based on the measurement of velocity and vortex added-mass in the animal wake. The model is contingent on the identification of the vortex boundary in the wake. This paper demonstrates the application of that method to a case study quantifying the instantaneous locomotive forces generated by the pectoral fins of the bluegill sunfish (Lepomis macrochirus Rafinesque), measured using digital particle image velocimetry (DPIV). The finite-time Lyapunov exponent (FTLE) field calculated from the DPIV data was used to determine the wake vortex boundary, according to recently developed fluid dynamics theory. Momentum of the vortex wake and its added-mass were determined and the corresponding instantaneous locomotive forces were quantified at discrete time points during the fin stroke. The instantaneous forces estimated in this study agree in magnitude with the time-averaged forces quantified for the pectoral fin of the same species swimming in similar conditions and are consistent with the observed global motion of the animals. A key result of this study is its suggestion that the dynamical effect of the vortex wake on locomotion is to replace the real animal fin with an `effective appendage', whose geometry is dictated by the FTLE field and whose interaction with the surrounding fluid is wholly dictated by inviscid concepts from potential flow theory. Benefits and limitations of this new framework for non-invasive instantaneous force measurement are discussed, and its application to comparative biomechanics and engineering studies is suggested.

Key words: swimming, force, locomotion, fish, particle image velocimetry, pectoral fin, vortex, fluid dynamics

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				J. Peng and J. O. Dabiri The `upstream wake' of swimming and flying animals and its correlation with propulsive efficiency J. Exp. Biol., August 15, 2008; 211(16): 2669 - 2677. [Abstract] [Full Text] [PDF]

				J. Peng and J. O. Dabiri An overview of a Lagrangian method for analysis of animal wake dynamics J. Exp. Biol., January 15, 2008; 211(2): 280 - 287. [Abstract] [Full Text] [PDF]

				R. Holzman, S. W. Day, and P. C. Wainwright Timing is everything: coordination of strike kinematics affects the force exerted by suction feeding fish on attached prey J. Exp. Biol., October 1, 2007; 210(19): 3328 - 3336. [Abstract] [Full Text] [PDF]