EXPERIMENTAL-STUDY OF 3-DIMENSIONAL WAVE BREAKING

The present study investigates two cases of three-dimensional wave bre aking. In the first case, the wave field contains a single frequency w ith a uniform angular spreading within a given range {-alpha, alpha). The wave field of the second case consists of a number of frequencies with a uniform angular spreading applied to each frequency. In both ca ses, the waves arc designed such that the wave energy is focused at a given point. Surface elevation in the focusing region is recorded and parameters such as the breaking-wave height and the crest-front steepn ess are calculated. It is shown that the wave height, crest elevation, crest-front steepness, and vertical asymmetry factor, at breaking, ar e strong functions of the angular spreading, while the crest-rear stee pness and horizontal asymmetry factor are little affected by the angul ar spreading. In general, the greater the spreading angle, the bigger are the breakers. It is hoped that the results obtained here will prov ide a useful preliminary assessment of the importance of three-dimensi onality in wave breaking.