3D CFD Modelling of Hopper Sedimentation
CEDA Dredging Days 2019
L. de Wit
Abstract: A 3D multiphase Navier Stokes CFD (Computational Fluid Dynamics) model is presented which is capable to simulate hopper sedimentation. Vertical and horizontal variations in velocity, slurry concentration, bed level and production/overflow pipe location are fully taken into account. Polydisperse hindered settling is included. Erosion and sedimentation of the hopper bed is simulated including dynamic bed update. The result of the model is 4D (x,y,z,t) information on SSC (suspended sediment concentration), velocities inside the hopper and bed height and PSD inside the bed during loading of the hopper. Also, the time evolution of quantity and PSD of overflow losses is predicted. Sloping V or W shaped hopper bottoms can be taken into account. Multiple production inflow pipe and/or overflow locations can be simulated at any desired location in the hopper and the inflow can be stationary or transient in time. Additionally, it is possible to move overflow locations vertically and switch specific production inflow pipes on or off in time or as function of the bed level inside the hopper.
The presented 3D CFD model for hopper sedimentation is useful to predict hopper loading and overflow losses in the preparation phase of projects and can be used to find the influence of different source sediment characteristics, different hopper characteristics, different productions, different loading configurations or different overflow configurations. Not only hopper loading can be simulated with this CFD model but also ballasting of a GBS (Gravity Based Structure), ballasting a caisson or even a very large-scale case as a land reclamation.
In this paper the 3D CFD hopper sedimentation model is introduced, results are compared to hopper sedimentation measurements and a realistic application case of loading a 15000 m3 TSHD is presented.
Keywords: 3D simulation, CFD, TSHD, hopper, sedimentation, overflow