Strongly coherent dynamics of stochastic waves causes abnormal sea states

Abstract

The dynamic kurtosis (i.e., produced by the free wave component) is shown to contribute essentially to the abnormally large values of the surface displacement kurtosis, according to the direct numerical simulations of realistic sea waves. In this situation the free wave stochastic dynamics is strongly non-Gaussian, and the kinetic approach is inapplicable. Traces of coherent wave patterns are found in the Fourier transform of the directional irregular sea waves; they strongly violate the classic dispersion relation.