||Sediment flushing of reservoir is an operational technique, whereby previously accumulated sediments in reservoirs are hydraulically removed by accelerated flow when the bottom desilting outlets of the dam are opened.
In this study, the process of sediment flushing is simulated in three dimensional domain of water reservoirs. A finite volume (FV) numerical model solves the Reynolds Averaged Navier Stokes (RANS) equations on a three dimensional grid. A RNG K- turbulence model is used.
The resulting flow field is used as input data for the sediment model. The convection diffusion equation for the sediment concentration is solved. The concentration equation derived by Van Rijn (Van Rijn L.C., Journal of Hydraulic Engineering, 1984) is adopted as a boundary condition, resulting in a calculation of bed material load. The depth integrated mass balance equation is applied to find the bed changes.
The results from the numerical model were compared with data from physical model studies available in literature (Lai J.S. and Shen H.W., International Journal of Sediment Research, 1995). The deviation between the calculated and measured data was small. This shows that the simplifications made in the numerical model are reasonable.
Results show that volume of sediment flushed is related to the outflow discharge, initial conditions of water level and inflow sediment concentration.