EXPERIMENTAL INVESTIGATION OF WAVE-PROPAGATION OVER A BAR

Laboratory experiments have been performed to elucidate the phenomenon of high frequency energy generation observed in the power spectra of waves traveling over submerged bars. Wave breaking itself, even in the case of plunging breakers. is found to be a secondary effect in this process, contributing by dissipating the overall wave energy without changing its relative spectral distribution significantly. The dominant physical mechanism is the amplification of the bound harmonics during the shoaling process, and their release in the deeper region, resulting in the decomposition of these finite amplitude waves. The observations suggest the feasibility of numerical modeling of the harmonics generation and release in breaking waves on the basis of a model for nonlinear conservative (non-dissipative) wave-wave interaction, to simulate the evolution of the spectral shape, in conjunction with a (semi-empirical) model for the dissipation of the total energy due to breaking.