2-D MODELS FOR SUSPENDED SEDIMENT TRANSPORT - COMPARATIVE USE FOR THE CASE OF PTUJ LAKE

摘要

A comparison of 2-D models for flow and sediment transport simulations ispresented in the paper. PCFLOW2D and TCONC of the University of Ljubljanamodel steady flow on a rectangular grid while Rubar 20 of CEMAGREF can treatunsteady flow on an irregular curvilinear grid. Shallow water equations andadvection diffusion equation for suspended sediment transport are solvednumerically by the control volume method. The main differences between bothmodels are that PCFLOW2D uses a depth-averaged version of the k-e turbulentmodel while Rubar 20 keeps turbulent viscosity and diffusion coefficients constant.Formulations of the source term describing the exchange of sediments are alsoslightly different. Both models were compared on the real case of Ptuj Lake which isa reservoir on the River Drava near the town Ptuj in the North East of Slovenia. Afterthe models were calibrated with velocity and sediment deposition measurementsfrom 1981, 1991 and 1993, three different calculations were performed: PCFLOW2Don a rectangular grid of 25 by 50 m, Rubar 20 on the same grid and Rubar 20 on agrid fitted to the lake banks. Comparison of both models showed a similarity in thewater levels and velocity fields although locally some differences appear due todifferent interpolations of the bottom topography. For deposits the similarity is not soobvious because of three main causes that were identified: deviation inhydrodynamic results, differences in numerical solvers and different computations ofthe source term. The calibration of the parameters of this source term is the mostdifficult and time consuming task.