2D Modelling of turbulant transport of cohesive sediments in shallow reservoirs
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2006.
Modelling of the transport of fine cohesive sediments, as found in most South African reservoirs, has not been well developed. This is because the transport processes that are involved are complex and the theories not as implicit as the traditional equilibrium transport theories for coarse non-cohesive sediment. Advection and dispersion are found to be the processes that best describe the transport of fine sediments in turbulent flow conditions. A two-dimensional modelling tool, MIKE 21C, which simulates reservoir hydrodynamics and cohesive sediment transport processes with an advection-dispersion model, was evaluated in this thesis. The creation of such a numerical model involves the setting up of a suitable curvilinear grid and requires data on the bathymetry, recorded inflows as well as water levels. It also requires sediment characteristic parameters and transport parameters. These parameters have to be specified by the user based on previous studies and field measurement data. MIKE 21C was applied to laboratory flume tests and reservoir case studies in the field in order to determine the effects that these parameters have on the sediment transport in a series of sensitivity studies. Ranges were determined within which these parameter values should fall. A procedure was also developed through which reservoir sedimentation models can be calibrated.