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Three-dimensional vortex structures under breaking waves

Published online by Cambridge University Press:  02 December 2005

YASUNORI WATANABE
Affiliation:
Division of Environment and Resources Engineering, Hokkaido University, N13 W8, Sapporo 060-8628, Japan
HIROSHI SAEKI
Affiliation:
Division of Environment and Resources Engineering, Hokkaido University, N13 W8, Sapporo 060-8628, Japan
ROGER J. HOSKING
Affiliation:
Faculty of Science, Universiti Brunei Darussalam, Gadong BE1410, Brunei Darussalam

Abstract

The large-scale vortex structures under spilling and plunging breakers are investigated, using a fully three-dimensional large-eddy simulation (LES). When an overturning jet projecting from the crest in a breaking wave rebounds from the water surface ahead, the vorticity becomes unstable in a saddle region of strain between the rebounding jet and a primary spanwise vortex, resulting in spanwise undulations of the vorticity. The undulations are amplified on a braid in this saddle region, leading to a vortex loop with counter-rotating vorticity. This vortex loop consequently envelops adjacent primary vortices, to form a typical rib structure. This rib component (the stretched vortex loop) in the large-scale vortex structure, which intensifies in the strains associated with the multiple primary vortices generated throughout the splash-up cycle, appears to be the previously found obliquely descending eddy.

Type
Papers
Copyright
© 2005 Cambridge University Press

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