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Longshore motion due to an obliquely incident wave group

Published online by Cambridge University Press:  20 April 2006

S. C. Ryrie
S. C. Ryrie
Affiliation:
School of Mathematics, University of Bristol Present address: Department of Computer Studies and Mathematics, Bristol Polytechnic, Bristol BS16 1QY.
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Abstract

We consider longshore motion generated within the surf zone by obliquely incident breaking waves, and seek to describe the effect on such motion of variations, caused by wave grouping, in the incident longshore momentum flux. The effects of associated variations in set-up are not considered.

We use the linear long-wave equations to describe the motion resulting from the longshore momentum contained in a wave group. This consists of a succession of edge waves which disperse along the beach, and, for the example considered, an eventual steady circulation cell at the position of the wave group. We suggest that such a cell is always likely to be formed if the wave group is sufficiently localized, and that higher-modenumber edge waves are more likely to be excited.

We find timescales for the dispersal of the edge waves, and for the decay, due to bottom friction, of the circulation cell: we suggest that the latter may more generally be used, as a timescale for the effect of friction on longshore motion.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 137 , December 1983 , pp. 273 - 284
Copyright
© 1983 Cambridge University Press

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