3D CFD modelling of reservoir sedimentation pressure flushing at hydropower dams

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Résumé

This paper investigates local sediment flushing under pressure at dams through a low-level outlet for the control of reservoir sedimentation to protect the hydropower turbines. A state-of-the-art three dimensional fully hydrodynamic computational fluid dynamic (CFD) model was developed with user defined functions which link the sediment mass balance with the hydrodynamics in each time step, to simulate the formation of the local scour hole forming at the low level intake at the dam, as well as the sediment transport of the re-suspended non-cohesive sediment particles from the bed. The model was calibrated against a physical model with a movable bed. The 3D CFD model indicates that the scour hole shape is similar to the one observed during the physical model test, which gives confidence in the future use of CFD models to simulate such complex flow and sediment dynamics. The CFD model was subsequently used to determine the minimum hydro power plant (HPP) intake invert level for
which no coarse sediment will be entrained during sediment flushing through the low level outlet.

Mots-clés

hydropower dam; hydrodynamics; sedimentation; CFD model; sediment flushing