Surface Dispersion in Wave Flume

The surface dispersion of a floating bead under wave action was investigated by measuring the Lagrangian characteristics using photographic techniques. The experiments were carried out with regular waves in a wave flume where the water depth and the wave period were kept constant, and the wave height was varied. In the experiments, trajectories of the floating bead were recorded as a function of time by a movie camera. The analysis was restricted to the component of dispersion in the transverse direction only. The motion of the beads in an oscillatory flow was shown to be governed by a linear second-order differential equation. Starting from the fundamental principles, dispersion coefficients were investigated; statistical descriptions of the displacement and velocity fluctuations were obtained in time and length scales.