The flow in the surf zone: a fully nonlinear Boussinesq-type of approach

The dynamics of the wave propagation within the surf zone is represented through a weakly dispersive fully nonlinear Boussinesq-type of model. The flow is assumed rotational and the governing equations are derived with no assumptions on the order of magnitude of the nonlinear effects. In the modeling, the velocity field is influenced by the effects of vorticity due to breaking, and the vorticity transport equation is solved analytically. The amount of vorticity introduced by the breaking process is determined through an analogy with the hydraulic jump and the adoption of the concept of the surface roller. A numerical accurate description of the effects of the surface roller is obtained by adopting an original self-adaptive-time-varying grid, developed on purpose. Such an approach makes it possible to get a better resolution in the region with rapid variations where the vorticity is generated, without heavily affecting the efficiency of the numerical model. Comparisons with a weakly nonlinear version of the model show that the proposed model considerably improves the estimate of the dynamics of wave propagations both in the shoaling and in the surf zone. Comparisons with laboratory measurements, both for regular and irregular waves, demonstrate that the proposed model has fairly good prediction capabilities. In particular, in contrast to other models, it provides quite good estimates of both the velocity and the undertow profiles. Moreover, typical features of random wave breaking (such as varying breaking line, different wave height decay, effects of groupiness) can be reproduced by the proposed model, as shown through comparisons with groupy wave laboratory data. (c) 2005 Elsevier B.V. All rights reserved.