| In order to assess hydrodynamic boundary conditions for the design and maintenance of coastal structures in harbours and coastal regions, a new Boussinesq-type wave model is developed. An important aspect of numerical models is the treatment of boundary conditions. This also applies to the Boussinesq-type wave model TRITON. Two types of boundaries may be identified: open boundaries (also called seaward boundaries), necessary to limit the size of the computational domain, and closed boundaries, representing a beach, a dike, a revetment, a quay or a breakwater. Depending on the boundary geometry and wave field, waves reflect fully or partially at closed boundaries. Because the model TRITON employs a Cartesian grid, closed boundaries often do not run parallel to the gridlines. Accurate and robust numerical treatment of such boundaries is therefore necessary. In order to achieve this, we have developed a new technique which is as accurate as frequently used cutcell techniques yet much easier to implement. This new technique embodies the extrapolation of the boundary condition from the true, physical boundary to a boundary that fits the Cartesian grid (a staircase boundary). This method can, in principle, also be applied in other numerical wave models. The implementation of the boundary conditions mentioned above is an essential step towards applications of wave modelling in harbours. An example is provided of an application of waves entering a harbour with two breakwaters. |
