The numerical model SKYLLA, developed for simulation of breaking waves on coastal structures is described. The model is based on the Volume Of Fluid method and solves the two-dimensional (2DV) Navier-Stokes equations. Weakly reflecting boundary conditions allow waves to enter and leave the computational domain. Impermeable boundaries can be introduced to simulate a structure. A two-model approach can be used to simulate overtopping over a low crested structure. Results obtained with the model are compared with those obtained with physical model tests for waves on a 1:20 slope of a submerged structure.

A numerical model that can simulate plunging waves on permeable structures is described. The 'Volume Of Fluid' method is used to solve the two-dimensional (2D-V) incompressible Navier-Stokes equations. After implementation of porous media flow for applications with permeable structures, the model has been verified by using several analytical solutions and by comparisons with physical model tests to study breaking waves on and inside permeable structures.