EXPERIMENTAL-STUDY OF 3-DIMENSIONAL BREAKING WAVE KINEMATICS

Particle image velocimetry has been used to examine three-dimensional breaking wave kinematics. Two cases of wave breaking were studied. In the first case, the wave field contains a single frequency with a unif orm angular spreading within a given range {-alpha, alpha}. The wave f ield of the second case consists of a number of frequencies with a uni form angular spreading applied to each frequency. In both cases, the w aves are designed such that the wave energy is focused at a given poin t. The degree of angular spreading has been found to have great effect :; on the breaking characteristics and kinematics. Two types of breake r were observed, the first being plunging and the second being spillin g. Increasing the angular spreading had the effect of making the veloc ities within the extreme waves larger. The ratio of the crest velocity to the breaking wave speed was approximately unity under both single and multiple frequency conditions, regardless of the angular spreading . (C) 1998 Elsevier Science Limited. All rights reserved.