132 / 2024-02-18 19:22:23

Modelling of Sediment Clump Dynamics in Open Water Disposal

sediment,sediment clump,sediment plume,numerical modelling

With the rapid growth of population and economy in coastal cities worldwide, dredging and land reclamation have become vital activities to facilitate maritime industry navigation and infrastructure expansion. However, open water disposal of sediment during these processes presents significant environmental concerns, particularly regarding the loss of suspended sediment and the accuracy of sediment placement. To address these issues, understanding near-source sediment dynamics is crucial for engineering assessment.



In current literature, the disposed sediment is often modelled as a group of dense particles released instantaneously into water, forming a circulating vortex sediment cloud, holding the particles together while descending. However, this may not accurately represent the actual scenario, especially when finer sediments are involved, leading to the formation of sediment clumps. These clumps feature a fast descending sediment core, with sediments shedding along its path, posing a greater threat to the environment as larger amounts of sediments become suspended in the water column.



Despite the importance of sediment clump behaviour, comprehensive studies in this area are lacking. This study proposes a new mathematical model based on force balance to assess sediment clump behaviour. The model accounts for three key aspects of sediment clumps: the fast settling of the front core, sediment shredding due to the lee-side vortices, and the lateral spreading of the shredded sediment.



The sediment shedding is a critical aspect of the model, determining the sediment mass in the front core. It is modelled as a function of Cloud Number, a dimensionless parameter governing disposed sediment formation. The model is calibrated using experimental data to validate its accuracy and reliability. The results demonstrate the effectiveness of the proposed model in predicting sediment clump dynamics and provide valuable insights for optimizing open water sediment disposal strategies and mitigating environmental impacts.