STRUCTURE OF FREQUENCY DOMAIN MODELS FOR RANDOM WAVE BREAKING

James T. Kirby, James M. Kaihatu

Abstract


We consider the form of a breaking wave dissipation term for use in spectral or stochastic wave evolution models. A time-domain Boussinesq model is tested for accuracy in modelling evolution of second and third moment statistics in shoaling and breaking waves. The structure of the dissipation term in the time domain is then used to infer the corresponding structure of the term in the frequency domain. In general, we find that the dissipation coefficient is distributed like l/S^(f), where Sv(f) is the spectral density of the surface displacement rj. This implies an /2 dependence for the coefficient in the inner surfzone, as opposed to a constant distribution over frequency as suggested by Eldeberky and Battjes (1996).

Keywords


frequency domain; model structure; random waves; wave breaking

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