Abstract: It is essential to effectively reduce the generation of turbidity and pollution in dredging works. In this paper, the flow field during the drop of a sealed grab bucket was simulated with a three-dimensional coupled fluid-structure-sediment-seabed interaction model (FS3M), and the impact of different drop modes on turbidity was discussed in order to propose the optimal drop operation for reducing the turbidity effectively. Numerical results showed that a decrease in the drop speed of the bucket could effectively reduce flow velocity at the bottom, suggesting a reduction in the generation of turbidity from the bottom. In particular, reducing the drop speed of grab bucket to one-third at 3 meters from the bottom is found to be the most effective.

Key words: dredging, grab bucket, drop operation, flow field disturbance, numerical analysis, water turbidity