A NUMERICAL STUDY OF BREAKING WAVES AND A COMPARISON OF BREAKING CRITERIA

A fully nonlinear 2-dimensional numerical wave flume, based on a boundary integral equation method, has been developed for studying waves at the instant that they break. The flume is used to study monochromatic and multiple frequency energy focussed waves breaking in deep water, and waves breaking due to shoaling over a range of slopes. For each breaking event the geometric and kinematic wave breaking parameters are recorded and examined in detail. It is shown that breaking criteria based on wave steepness are not always applicable, and that criteria based on the particle velocities are only likely to be true for theoretical Stokes' waves. The minimum vertical and maximum horizontal Lagrangian accelerations at breaking are found to be independent of the parameters with which they are compared, with constant values of -g and 1.54g, respectively. It is therefore concluded, that there exists a universally applicable breaking criterion based on these values for the Lagrangian accelerations.