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Hydrodynamic stability of swimming in ostraciid fishes: role of the carapace in the smooth trunkfish Lactophrys triqueter (Teleostei: Ostraciidae)

Bartol, Ian K. and Gharib, Morteza and Wiehs, Daniel and Webb, Paul W. and Hove, Jay R. and Gordon, Malcolm (2003) Hydrodynamic stability of swimming in ostraciid fishes: role of the carapace in the smooth trunkfish Lactophrys triqueter (Teleostei: Ostraciidae). Journal of Experimental Biology, 206 (4). pp. 725-744. ISSN 0022-0949. doi:10.1242/jeb.00137.

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The hydrodynamic bases for the stability of locomotory motions in fishes are poorly understood, even for those fishes, such as the rigid-bodied smooth trunkfish Lactophrys triqueter, that exhibit unusually small amplitude recoil movements during rectilinear swimming. We have studied the role played by the bony carapace of the smooth trunkfish in generating trimming forces that self-correct for instabilities. The flow patterns, forces and moments on and around anatomically exact, smooth trunkfish models positioned at both pitching and yawing angles of attack were investigated using three methods: digital particle image velocimetry (DPIV), pressure distribution measurements, and force balance measurements. Models positioned at various pitching angles of attack within a flow tunnel produced well-developed counter-rotating vortices along the ventro-lateral keels. The vortices developed first at the anterior edges of the ventro-lateral keels, grew posteriorly along the carapace, and reached maximum circulation at the posterior edge of the carapace. The vortical flow increased in strength as pitching angles of attack deviated from 0°, and was located above the keels at positive angles of attack and below them at negative angles of attack. Variation of yawing angles of attack resulted in prominent dorsal and ventral vortices developing at far-field locations of the carapace; far-field vortices intensified posteriorly and as angles of attack deviated from 0°. Pressure distribution results were consistent with the DPIV findings, with areas of low pressure correlating well with regions of attached, concentrated vorticity. Lift coefficients of boxfish models were similar to lift coefficients of delta wings, devices that also generate lift through vortex generation. Furthermore, nose-down and nose-up pitching moments about the center of mass were detected at positive and negative pitching angles of attack, respectively. The three complementary experimental approaches all indicate that the carapace of the smooth trunkfish effectively generates self-correcting forces for pitching and yawing motions — a characteristic that is advantageous for the highly variable velocity fields experienced by trunkfish in their complex aquatic environment. All important morphological features of the carapace contribute to producing the hydrodynamic stability of swimming trajectories in this species.

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Additional Information:© The Company of Biologists Ltd 2003. Accepted 11 November 2002. We thank R.M. Alexander and P. Krueger for valuable intellectual input, M. McNitt-Gray, J. Carnahan, B. Valiferdowsi, and P. Masson for aid during model construction, D. Lauritzen and S. Bartol for assistance during data collection, and D. Dabiri, L. Zuhal, and D. Jeon for technical assistance. Smooth trunkfish were collected by W. Rosado, Department of Marine Science, University of Puerto Rico-Mayaquez. Financial support of the Office of Naval Research under contract N00014-96-0607 (to M.S.G. and M.G.) is gratefully acknowledged.
Funding AgencyGrant Number
Office of Naval ResearchN00014-96-0607
Subject Keywords:boxfish, Lactophrys triqueter, stability, hydrodynamics, swimming, pressure, particle image velocimetry, moment
Issue or Number:4
Record Number:CaltechAUTHORS:BARjeb03
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11900
Deposited By: Archive Administrator
Deposited On:09 Oct 2008 05:06
Last Modified:08 Nov 2021 22:22

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