Numerical and experimental modelling of near-field overflow dredging plumes

Turbidity plumes are an important topic in the environmental aspects of dredging. Turbid sediment plumes can cause damage when they reach environmentally sensitive areas such as coral reefs, sea grass fields and wetlands. The main source of turbidity while employing Trailer Suction Hopper Dredgers is the release of excess water through the overflow shaft. In order to minimise environmental impacts of turbidity in early stages of planning as well as during project execution, turbidity prediction tools are necessary. To this end, numerical modelling tools are the most effective in the prediction of the sea currents and sediment dispersion. The near field plume dynamics below and directly behind the sailing hopper dredgers has always been the weakest link in these predictions, since accurate input of the vertical and horizontal distributions of sediment at the source location are paramount to obtain reliable results at the environmentally sensitive areas further away. In this research, physical and numerical modelling are used as a tool to determine the three-dimensional flows of water, sediment and air bubbles directly after release from the overflow shaft. A full dredger hull geometry and an actuator disk accounting for propeller action will add to the representation of the complexity of the flow. The goal of the research is to improve the predictions of dredging-induced turbidity in the planning phase. In this way, modifications of the dredging operations can be made in order to reduce the environmental impact.nrpages: 312status: publishe

Mean and fluctuating suspended sediment concentration measurements using ADV

The present experimental research looks for ways to improve fine sediment transport measurements with ADV by further investigating the factors influencing the backscatter intensity of the acoustic wave. The optimal instrument settings are determined in order to maximally extend the region of increasing response to fine suspended sediments in the sampling volume and a spectral correction is used to obtain turbulent sediment concentration fluctuations

A continental shelf model in TELEMAC 2D

Water Qualit

CouplingTELEMAC-3D with the General Ocean Turbulence Model (GOTM)

Water Qualit

Experimental investigation of negatively buoyant sediment plumes resulting from Dredging operations

In a first step to investigate the behaviour of sediment plumes released from dredging vessels, an experimental facility has been built to release scaled fine sediment plumes in the presence of cross flow. High-frequency measurements of velocity components and sediment concentration are obtained using acoustic and optical backscatter instruments. The paths of the axis of the experimental buoyant plumes in cross-flow have been compared to integral laws by Fisher et al. (1979), showing relatively good agreement for plumes not influenced by the dredger’s hull. Plumes with low relative density difference and high crossflow to outflow velocity ratio deviate from the integral laws due to additional mixing induced by the hull boundary layer and wake

Modelling the Eddy Pattern in the harbour of Zeebrugge

Hydrodynamic

A regional model for South East Asia in TELEMAC 2D

Water Qualit

Large-Eddy Simulations of a Sediment-Laden Buoyant Jet Resulting from Dredgers Using Overflow

Interaction between Offshore Utilisation and the Environmen

Improvement of a Continental Shelf Model of the North Sea

Hydrodynamic

A TELEMAC-2D model for the Indian Ocean, Persian Gulf and Red Sea with a special focus on the tidal body force

Water Qualit