Three-dimensional numerical modelling of bed changes in a sand trap
Three-dimensional numerical modelling of bed changes in a sand trap
Abstract
Water and sediment flow was modelled numerically in three dimensions
in a tunnel-type sand trap. The numerical model solved the transient
Navier-Stokes equations with the k-e turbulence model. Simultaneously,
the sediment flow was calculated by solving the transient
convection-diffusion equation for sediment concentration. Multiple
sediment sizes were used. Van Rijn's formula for sediment concentration
was used as boundary condition for the bed. Sediment continuity for the
cells close to the bed gave the bed changes with time. An adaptive grid
was used, adjusting to the bed changes. The processes in the sand trap
involved both sedimentation and erosion, as a large volume of sand were
formed and moved through the geometry. A physical model test was carried
out to verify the numerical model. Bed levels were measured at a
longitudinal profile and a cross-section. The results from the physical
and numerical model compared well.