Abstract
This study first investigated the possibility that sands can serve as tracer particles in PIV (particle image velocimetry). Then we conducted hydraulic model tests on a movable bed for investigating migration velocities of suspended sediments associated with breakers. We further carried out numerical simulation using a κ-ε model to determine the correlation between the migration velocities of sands and the numerically-simulated velocity fields and vortex structures under the waves. We found that the sedimentation speed of silica sands derived from the PIV method is comparable to the sedimentation speed of sediments calculated by Rubey's formula, confirming that silica sands can serve as tracer particles in the PIV method. We also found that the migration velocities of sediments become faster than the water particle velocities where the water under wave motions moves in the same direction as the sedimentation direction of sands, thereby reinforcing one another; on the other hand, the migration velocities of sediments become slower than the water particle velocities where the water under wave motions moves in the direction opposed to the sedimentation direction of sands, thereby interfering destructively.
