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C-start: optimal start of larval fish

Published online by Cambridge University Press:  03 February 2012

M. Gazzola
Affiliation:
Institute of Computational Science, ETH Zürich, Universitätsstrasse 6, CH-8092 Zürich, Switzerland
W. M. Van Rees
Affiliation:
Institute of Computational Science, ETH Zürich, Universitätsstrasse 6, CH-8092 Zürich, Switzerland
P. Koumoutsakos*
Affiliation:
Institute of Computational Science, ETH Zürich, Universitätsstrasse 6, CH-8092 Zürich, Switzerland
*
Email address for correspondence: petros@inf.ethz.ch

Abstract

We investigate the C-start escape response of larval fish by combining flow simulations using remeshed vortex methods with an evolutionary optimization. We test the hypothesis of the optimality of C-start of larval fish by simulations of larval-shaped, two- and three-dimensional self-propelled swimmers. We optimize for the distance travelled by the swimmer during its initial bout, bounding the shape deformation based on the larval mid-line curvature values observed experimentally. The best motions identified within these bounds are in good agreement with in vivo experiments and show that C-starts do indeed maximize escape distances. Furthermore we found that motions with curvatures beyond the ones experimentally observed for larval fish may result in even larger escape distances. We analyse the flow field and find that the effectiveness of the C-start escape relies on the ability of pronounced C-bent body configurations to trap and accelerate large volumes of fluid, which in turn correlates with large accelerations of the swimmer.

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Papers
Copyright
Copyright © Cambridge University Press 2012

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Gazzola et al. supplementary movie

Vorticity fields of the 2D best solution found during the optimization (blue -negative- and red -positive- vorticity ω)

Download Gazzola et al. supplementary movie(Video)
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Supplementary material: PDF

Gazzola et al. supplementary material

Appendix

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PDF 226.9 KB

Gazzola et al. supplementary movie

Vorticity fields of the 3D best solution found during the optimization (isosurfaces are based on vorticity magnitude | ω |, while the coloring blue -negative- and red -positive- is based on the z-component of ω)

Download Gazzola et al. supplementary movie(Video)
Video 5.1 MB