Bed changes in a tunnel sand trap

Bed changes in a tunnel sand trap

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)

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This page was last updated: 25 March 1997