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Hydrodynamics of locomotion in the squid Loligo pealei

Published online by Cambridge University Press:  22 June 2001

ERIK J. ANDERSON
Affiliation:
Biology Department, St. Francis Xavier University, PO Box 5000, Antigonish, Nova Scotia, Canada B2G 2W5 Present address: Department of Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
WILLIE QUINN
Affiliation:
Engineering Department, St. Francis Xavier University, PO Box 5000, Antigonish, Nova Scotia, Canada B2G 2W5
M. EDWIN DE MONT
Affiliation:
Biology Department, St. Francis Xavier University, PO Box 5000, Antigonish, Nova Scotia, Canada B2G 2W5

Abstract

Potential flow analysis, including unsteady effects, has been applied to live swimming squid, Loligo pealei. Squid were modelled as slender, axisymmetric bodies. High-speed video records, recorded at frame rates of 125 to 250 Hz, provided time-varying body outlines which were digitized automatically. Axisymmetric renderings of these body outlines and the real motion of the squid were used as the input of the potential flow analysis. Axial and lateral inviscid fluid forces simply due to the flow past the squid body were calculated from pressures coefficients obtained from the unsteady Bernoulli equation. Lateral forces were found to play virtually no role in determining muscle stresses in squid jet propulsion. Axial pressure forces were also found to be small in comparison to both net force (based on the observed whole body kinematics) and estimations of skin friction. These findings demonstrate the effects of the highly adapted shape of squid with regard to hydrodynamics. The work suggests that skin friction and working fluid intake are the most significant sources of drag on a swimming squid.

Type
Research Article
Copyright
© 2001 Cambridge University Press

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