A comparison of simple buoyant jet models with CFD analysis of overflow dredging plumes

Trailing Suction Hopper Dredgers release excess water with a varying flow rate and with variable fine sediment content. In the recent past, the near-field dispersion of overflow dredging plumes was determined using simple integral solutions or Lagrangian models of the buoyant jet in cross flow. In reality, these negatively-buoyant sediment plumes are interacting with the flow around the hull of the vessel, air bubbles and the propellers. If these interactions are not taken into account for the near-field modelling, the source terms for far-field simulations of the environmental impact of turbidity are inaccurate. By consequence, the predictions of the environmental impact of the generated turbidity might not be accurate enough to avoid adverse effects later on in the project phase. In a CFD analysis, it is investigated how these complex interactions take place and how they can be included in near-field dredging plume simulations. The CFD analysis reveals that the simple models can be relatively accurate in some cases, but that large deviations exist for most real-life situations.