Simulating turbidity plumes with OpenFOAM
CEDA Dredging Days 2017 - Sustainable Dredging - Continued Benefits
van Grunsven F., Keetels G.H., van Rhee C.
Abstract: Assessing the impact of turbidity plumes caused by offshore mining activities is a requirement to obtain an environmental permit. Constructing reliable and accurate predictions vital for obtaining an environmental permit, is however a complex process. A Dutch national research project aims to improve and expend the available tools to mitigate and asses the environmental impact caused by offshore mining. Improving predictions of turbidity plume developments caused by the deep sea discharge of mining tailings is a vital part of this research. The prediction of these turbidity plumes especially presents a complex fluid dynamical flow problem when interaction with the seafloor becomes important. However, recent advances in computational fluid dynamics (CFD) in combination with the increase in available computational processing power might offer a solution. It is suggested to extend an existing numerical solver capable of solving fluid flows near complex geometries such as a rough seabed or a complex diffuser. Open-source software OpenFOAM complies with this trade, and comes with full code transparency towards the community. The basic flow solver of OpenFOAM has recently been validated for the prediction of submerged turbulent discharges without gravity forces. These forces are however required for the intended application, as suspended sediment causes the turbidity plumes to descend as a negatively buoyant plume. This paper discusses the effectiveness of the chosen model for the prediction of turbidity plume behaviour. Several turbidity plume simulations are compared with experiments. Model adjustments are proposed, of which several are tested. Recommendations for further improvement are presented based on the results. In the near-future, the final model is used to simulate several discharge scenarios on which discharge guidelines can be established. The final aim is for the numerical model to serve as an alternative or supplement to experiments in the development phase of offshore mining projects.
Keywords: Turbidity plume modelling, Environmental Impact Assessments