Quantitative research on the characteristics of flow field structures after wave-breaking in deep water

Abstract

This paper presents the results of laboratory experiments conducted for quantitative research into the characteristics of flow field structures after wave-breaking in deep water. The influence of wave-breaking is generally considered as a source term in ocean models, and parameterization of the breaking process is based on feature analysis of the flow field structures after wave-breaking. The breaking waves are generated based on the wave-focusing method. Particle image velocimetry is used to measure the velocity of the flow field near the breaking point, and ensemble-averaging is adopted to analyze the stable characteristics of the flow field. These characteristics are related to the intensity of the wave-breaking, which is reflected in the wave energy loss induced by breaking. A quantitative relation is first established between the wave energy loss and the wave parameters. An expression is then derived, which expresses the vertical distribution of horizontal velocity as a function of the wave energy loss, water depth, and horizontal distance from the breaking point. The horizontal momentum-transport is calculated based on the time integral of the horizontal velocity and is found to reflect the effect of stress induced by wave-breaking. The quantitative results are shown to be in good agreement with the experimental data. The results directly link the velocity distribution after wave-breaking to the wave parameters in a concise way and support the parameterization of wave-breaking in ocean models.