Entin A. Karjadi, Nobuhisa Kobayashi


A time-dependent quasi-3D numerical model is developed to predict the temporal and cross-shore variations of the free surface elevation and fluid velocities in the surf and swash zones under obliquely incident waves. This model, which includes the dispersion due to the vertical variations of the instantaneous horizontal velocities, is an extension of the two-dimensional model of Kobayashi and Karjadi (1994, 1996). The developed model is compared with available laboratory and field data for planar beaches as well as field data for a barred beach. For planar beaches, the dispersion effects on the longshore current are significant for regular waves but secondary for irregular waves. For a barred beach, the model under the assumption of alongshore uniformity cannot predict the broad peak in the longshore current profile. The small alongshore variation of wave setup induced by a small alongshore variation of obliquely incident irregular waves is shown to significantly modify the driving force and longshore current profile in the bar trough region. On the other hand, for planar beaches, the alongshore current profile is shown to be insensitive to the small alongshore variation of obliquely incident waves. This may explain why existing longshore current models based on the assumption of alongshore uniformity were regarded to be adequate before their comparisons with the barred beach data.


breaking waves; quasi-3D model

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