Behavior of Sediment Clouds in Waves

Abstract

The effects of regular surface waves on the descent of instantaneously released sediments were investigated experimentally. The detailed wave characteristics, including wave height (H), wave period (T), and wave phase of release, were controlled systematically through a wave synchronization system. The results showed that the sediment cloud was passively advected by the wave orbital motion, and there was no significant phase lag between the sediments and surrounding water particles. The motion of the center of mass and the growth rate of the sediment cloud averaged over four representative wave phases of release were found to be similar to those in a stagnant ambient condition. However, a shift (in the range of ±H/2) in the horizontal equilibrium position of the oscillatory motion was observed and could be related to the wave phase of release. A passive advection model was proposed to predict the motion of a sediment cloud in the wave environment by superimposing the wave orbital velocity onto the descent velocity of the sediment cloud induced by buoyancy excess. The prediction was found to be in reasonable agreement with the experimental data.