Three-dimensional (3-D) Numerical Modelling of Flow and Sediment Deposition in Shallow Rectangular Reservoirs

Shallow reservoirs are widely used as storage basins for flood management or as silting basins for sediment trapping. Reliable predictions of flow and sediment deposition in reservoirs are necessary to achieve a cost-effective, sustainable planning of their management. The use of three-Dimensional (3D) numerical models is suitable for capturing the complex flow and sediment transport patterns encountered in shallow reservoirs. In this work, the 3D numerical model TELEMAC3D is used. The hydrodynamic computation is based on the solution of the Reynolds Averaged Navier-Stokes (RANS) equations with a non-hydrostatic pressure distribution. The continuity equations for the liquid and solid phases are written separately, and the water momentum balance is formulated for clear water. The sediment transport is based on the solution of the advection-diffusion equation. The turbulence stresses are computed with Boussinesq relations and a closure turbulence model. Resolution of the governing equations relies on a finite element method on an unstructured mesh. The 3D domain is obtained by extruding the 2D unstructured mesh along the vertical direction that exactly fits the bottom and the free surface. We simulate laboratory experiments and compare the numerical results to the measurements in terms of flow patterns, velocity field and bed changes due to sediment disposition. This work investigates also the role of the initial conditions, the location of the inlet and outlet channels of the reservoir as well as the role of the mesh and turbulence closure equation.