External and internal flow fields of plunging breakers

This first stage of a laboratory study of the turbulent flow-field induced by wave-breaking involves the application of a flow-visualization technique from which external appearance and internal flow-structures of the surf zone have been examined. Plunging breakers were generated in a wave flume, whilst suitable light sources were deployed. To trace the water particle motion, fluorescent coatings in combination with suitable illuminating light sources, such as an Argon-Ion laser and ultraviolet lamps, were used. Whilst a particular light source was suitable for studying the water body in the surf zone, it might not be for studying particle motion in the air-bubble zone having a high concentration of air entrainment. It was found that the motion in the surf zone was highly three-dimensional with a dividing region formed beneath the impinging surface rollers, and that the breaking phenomenon was cyclic and deterministic in character.