Modeling the Transformation of Nonlinear Waves Passing Over a Submerged Dike

The decomposition phenomenon of a nonlinear wave train passing over a submerged dike has been investigated by a previously developed numerical model. The model, based on the time-dependent boundary element method, employs an effective nonreflective open boundary treatment and can be applied to arbitrary nonlinear wave processes. The results for regular wave incidence indicate that the higher harmonics generated during passage over the dike are transformed into prominent free waves in the trailing side of the dike, revealing the essential mechanism of the observed decomposition phenomenon. The computed wave profiles at various locations agree favorably with experimental observations. The transformation of multicomponent random waves has also been investigated. The results show that a substantial amount of wave energy is transferred into higher frequency components. The power spectrum of the transmitted wave is found to be significantly influenced by the phase differences among the incident components as well as by the incident wave spectrum itself.