Surf-zone dynamics concerns the wave-wave and wave-mean-flow dynamics in that region of the beach where wave breaking occurs. The generation of longshore currents and horizontal eddies by breaking waves in the surf zone is analysed in a shallow-water framework augmented with bores and hydraulic jumps. The latter aim to model breaking waves in the surf zone. Firstly, it is shown that nonuniform bores in general generate potential vorticity, and hence eddy motion. This non-uniformity may be caused by irregular wave forcing at the seaward boundary, by irregular beach topography, or a combination thereof. Secondly, this potential vorticity generation mechanism is shown to yield an alternative explanation for rip current formation and longshore current formation by (obliquely incident) incoming waves or bores. This explanation will be supported through several numerical simulations.
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12th Conference on Atmospheric and Oceanic Fluid Dynamics