Simulation of Flow Hydraulics and Sediment Load in River Bends (Case Study: Karoun river)

Simulation of lateral distributions of velocity and suspended sediment concentration in river bends is of great significance, and has many applications for river engineering projects. Due to secondary flow development, flow structure in river bends has 3-dimensional nature. As shown in Fig. 1, the secondary flow, coupled with the longitudinal primary movement, causes a helical flow that forms in the river bend (Perkins, 1970). In this case, 1-dimensional mathematical models (e.g. HEC-RAS, MIKE-11 and ISIS) are generally not satisfactory and 2 or 3-dimensional mathematical models should be used instead. However, the large amount of computational time needed to simulate flow field in rivers by 3D or 2D mathematical models, justifies the use of quasi 2D modes. Among the numerous quasi 2D models, the Shiono and Knight model has attracted great attention of river engineers. This mathematical model is based on the depth averaged integration of Navier-Stocks equations. Due to suitable form of in this study, at first with field measurement of lateral distributions of velocity and suspended sediment concentration in three bends located at the Karoun river (namely Maliheh, Jangieh and Khabineh), the Shiono and Knight quasi-two dimensional model (1991) has been calibrated. Using the lateral velocity profiles obtained by this mathematical model, sediment transport capacities were computed. The results showed that in all three river bends, among the empirical sediment equations selected for this study, the sediment transport equation of Yang has very well agreement with the measured lateral suspended sediment concentration, in comparison to the Ackers-White and Engelund-Hansen equations.