Numerical simulation of erosion and sedimentation pattern in meandering channels with moving bed

Erosion and sedimentation in river arches cause problems in river structures. Therefore, the pattern of flow and transport of sediments in the open channels of meandering River has attracted the attention of river engineers. Since the flow field in the bends of rivers is three-dimensional, therefore, in the last few decades, the prediction of changes in bed level and changes in the location of banks with the help of computer programs has been given more attention.In this study, using SSIIM software, topographical changes of meandering channels with sinus generator and moving bed have been modeled, and bed level changes have been studied under different conditions. For this purpose, solid beaches Natural rivers are principal resources of water and energy. Design and operational management of natural rivers needs a complete knowledgement of mechanics of flow pattern and sediment transport. The complex three-dimensional flow characteristics inriver bends reveals the necessity of using a three-dimensional numerical model.The numerical model used in the present study is called SSIIM, an acronym for Sediment Simulation in Intakes with Multi block option. In this study, in the first step, SSIIM is applied to investigate the characteristics of turbulent flow in a Sine-Generated channel with 70-degree angle, the rectangular cross section of width B =40cm and fixed bed. In addition, a comparision has been also made between the turbulence models, the flow characteristics such as Longitudinal and transverse velocity, Water level and bed Shear stress has been considered. The results have been validated with laboratory data. The results show that SST-k-ω model has better consistency with experimental data than k-ε model. Also distribution of bed shear stress depends on Froude number although secondary flow is independent. Furthermore, distribution of bed shear stress and secondary flow is dependent on the width to depth ratio. For b/h<8, another circulation cell occurs near the outer bank.In the second step, to investigate the variation of channel bed subjected to steady flow, Channel with movable bed has been employed. Comparison of results show good agreement between computed and measured bed topography. Finally, the effective parameters including interval time step, grid size, Froude number, width to depth ratio and meandering angle has been investigated. Results show that by increasing the Froude number and the ratio of width to depth point bar and point pool gradually migrate downstream channel. Whereas by increasing meandering angle, point bar and point pool moving Upstream.