Influence of the vertical discretisation of SLIM 3D on a river plume modelling

Delandmeter, Philippe [UCL] Lambrechts, Jonathan [UCL] Remacle, Jean-François [UCL] Legat, Vincent [UCL] Wolanski, Eric [James Cook University, Townsville, Australia] Deleersnijder, Eric [UCL]

Unstructured-mesh models have shown their efficiency for coastal system modelling. Among these, SLIM 3D, a baroclinic discontinous Galerkin finite element model, has been recently applied to study the transport and fate of suspended sediment exported in a river plume. For such flows, SLIM 3D exhibits numerical dissipation where strong density gradients occur, especially on the vertical direction. One way to tackle this problem is to adapt the mesh resolution. SLIM 3D horizontal mesh is fixed, but vertical grid is moving. Different discretisation strategies are possible. During this presentation we will focus on the vertical discretisation of SLIM 3D. Different options will be presented: σ-layers, σ-layers on the bottom with z-layers on the top, or an adaptive vertical grid. We will show how those different strategies influence the sharpness of the freshwater front and the accuracy of the solution, through a simple testcase. Eventually, the influence of vertical discretisation on the Burdekin River Plume (Australia) simulation will be studied.