This is a calculation of bed changes in a tunnel-type sand trap (closed conduit, with no free surface). Time-dependent calculations of the 3D Navier-Stokes equations is done with the k-epsilon turbulence model. This is solved simultaneously with the convection- diffusion equation for sediment transport. Bed changes are also calculated over time, and an adaptive grid is used to modify the grid accordingly.

The result is the three-dimensional bed deposition/scour pattern at the bed of the sand trap. This is compared with results from a physical model test.

The graphics below shows the situation after 1 hour 20 minutes of sediment inflow. The sand trap is 5.2 meters long, has a maximum width of 25 cm and a maximum height of 31 cm. The water discharge is 15 l /s and the sediment inflow is 0.017 kg/s. The flow direction is from left to right. There is a main deposit from 2 - 3 meters downstream from the entrance of the sand trap.

The results from the numerial model correspond well with the measurements in a physical model (Olsen and Kjellesvig, 1997).

*The horizontal velocity seen from above, in a level midway between the bed and the roof
*

*The bed level seen from above
*

*The horizontal velocity in a longitudinal section at the centerline of the sand trap
*

*The sediment concentration in a longitudinal section at the centerline of the sand trap
*

(The black areas in the longitudinal profiles are the sediment deposits. The graphics images have been edited after generation with SSIIM to show these areas)

*This page was last updated: 25 March 1997*