Abstract
Sedimentation and erosion can significantly affect the performance of river regulated reservoirs. In the vicinity of flow control structures, the interaction between the hydrodynamics and sediment transport often induces complex morphological processes. It is generally very challenging to accurately predict these morphological processes in real applications. Details are given of the refinement and application of a three-dimensional (3-D) layer integrated model to predict the morphological processes in a river regulated reservoir. The model employs an Alternating Direction Implicit finite difference algorithm to solve the mass, momentum and suspended sediment transport conservation equations, and an explicit finite difference scheme for the bed sediment mass conservation equation for calculating bed level changes. The model is verified against experimental data reported in the literature. It is then applied to a scaled physical model of a regulated reservoir, including the associated intakes and sluice gates, to predict the velocity distributions, sediment transport rates and bed level changes in the vicinity of the hydraulic structures. It is found that the velocity distribution near an intake is non-uniform, resulting in a reduction in the suspended sediment flux through the intake and the formation of a sedimentation zone inside the reservoir.
Highlights
In order to better understand the impact of hydraulic structures on the hydrodynamic, sediment transport and morphological processes in reservoirs and rivers, it is often necessary to use numerical and/or physical models to investigate these dynamic and interacting processes
The numerical model predicted bed level changes at 6 cross–sections for case S.1 are shown in Fig. 1, together with the physical model results
At most locations the model predicted bed level changes were less than the measurements, but the predicted bed level change at L6-R6 was greater than the measured changes
Summary
In order to better understand the impact of hydraulic structures on the hydrodynamic, sediment transport and morphological processes in reservoirs and rivers, it is often necessary to use numerical and/or physical models to investigate these dynamic and interacting processes.The three dimensionality of turbulence and the sediment transport and morphological processes in the vicinity of hydraulic structures form a complex problem. van Rijn (1987) used a width-averaged two-dimensional numerical model to simulate bed level changes in a dredged trench. Olsen (1999) applied a 2-D depth-averaged numerical model to calculate bed level changes in a reservoir which was flushed by flood flows. Kocyigit et al (2005) presented the refinement of a 2-D depth-integrated numerical model for predicting the long-term bed level changes in an idealised model harbour. They reported an under-prediction of the depth of erosion, which was thought to be due to the model not correctly predicting the lateral movement of sediment
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