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چکیده
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Abstract Centrifugal force at the bend causes the terrain slope at water surface that increases water surface in outer arc and reduces in internal arc. This phenomenon creates adverse pressure gradient inside the arc of cross. As a result, a flow in the transverse direction within the cross is shaped that is called secondary flow. Secondary flow and its interaction with the inertia of the flow, which leads to create a spiral flow causes changes in the topography of the Bed. Understanding the topography of Bed in arcs is essential for specifying scour positions and sediments to determine the best location for the construction of hydraulic structures such as the groin, pond and rivers organizing management. Also in numerical models, one of the most important steps is meshing optimization to achieve the most accurate results and also the least time of analysis of model. Since investigating the numerical sediment transport has been very difficult and research in this area is little; In this study, the most optimal meshing in numerical model is investigated and then tried to be stimulated scouring in the channel bend 90°. For this purpose, the results of the topography of Bed within the arc of channel are obtained using the software FLOW3D and with different turbulence models and compared with experimental results. It should be noted that due to inability of software in the results in perpendicular sections and in direction of flow in the arc, neural network and genetic pattern was used for extracting numerical results in points matching laboratory results. Then flow field in arc is compared with experimental results. The results show the high ability of numerical model FLOW3D in simulating channel with moving Bed. The comparison of turbulence models indicates superiority of turbulence model of LES in investigating changes of Bed in arc channel to other turbulence models.
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