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Short‐crested waves in the surf zone
Author(s) -
Wei Zhangping,
Dalrymple Robert A.,
Xu Munan,
Garnier Roland,
Derakhti Morteza
Publication year - 2017
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2016jc012485
Subject(s) - breaking wave , surf zone , superposition principle , geology , wave shoaling , mechanical wave , wave setup , vorticity , potential vorticity , microseism , longitudinal wave , wave propagation , physics , mechanics , surface wave , rip current , wave height , geophysics , vortex , seismology , optics , oceanography , shore , quantum mechanics
This study investigates short‐crested waves in the surf zone by using the mesh‐free Smoothed Particle Hydrodynamics model, GPUSPH. The short‐crested waves are created by generating intersecting wave trains in a numerical wave basin with a beach. We first validate the numerical model for short‐crested waves by comparison with large‐scale laboratory measurements. Then short‐crested wave breaking over a planar beach is studied comprehensively. We observe rip currents as discussed in Dalrymple (1975) and undertow created by synchronous intersecting waves. The wave breaking of the short‐crested wavefield created by the nonlinear superposition of intersecting waves and wave‐current interaction result in the formation of isolated breakers at the ends of breaking wave crests. Wave amplitude diffraction at these isolated breakers gives rise to an increase in the alongshore wave number in the inner surf zone. Moreover, 3‐D vortices and multiple circulation cells with a rotation frequency much lower than the incident wave frequency are observed across the outer surf zone to the beach. Finally, we investigate vertical vorticity generation under short‐crested wave breaking and find that breaking of short‐crested waves generates vorticity as pointed out by Peregrine (1998). Vorticity generation is not only observed under short‐crested waves with a limited number of wave components but also under directional wave spectra.