Physical and coupled fully three-dimensional numerical modeling of pressurized bottom outlet flushing processes in reservoirs

Abstract

Sediment deposition in reservoirs is an important research topic in engineering practice. Reservoir sedimentation has the potential to affect flood levels, drainage for agricultural land, pump station and hydropower operation as well as navigation. This paper describes the development of a coupled fully three-dimensional (3D) numerical model for the prediction of the local sediment flushing scour upstream of the bottom outlet. The presented numerical model solves the Navier-Stokes equations in conjunction with the k- ɛ turbulence model which includes both sediment transport and hydrodynamic parameters. The proposed coupled fully 3D numerical model is used to simulate experimental tests based on non-cohesive sediment. The geometric features of the scour hole (temporal and spatial hole development) upstream of the bottom outlet were reasonably well predicted compared to the experimental data. Furthermore, the velocity field upstream of the bottom outlet was in good agreement with measurements. The proposed numerical model for bottom outlet flushing was, therefore, validated because of its ability to accurately predict the scour hole development during the flushing process. The proposed numerical model can be considered reliable provided that the model is correctly calibrated and set up to reflect the conditions of a particular case study.