Investigating the Bed Shear Stress Distribution in the Straight Compound Channels Using Numerical Simulation and Comparing the Results of Ansys Fluent and Flow-3D

The main difference between compound sections and simple sections in channels is due to the velocity difference between the floodplain and the main channel. This velocity change ultimately causes changes in the shear stress distribution of the bed canal. The structure of flow turbulence in compound channels is complex due to the combination of boundary shear stress and Reynolds stress near the interface of the floodplain and the main channel .Due to the fact that the flow hydraulics in rivers, which are considered to be a type of compound channel, depends on their shape and the changes in canal shape are dependent on bed shear stress, determining the distribution of bed shear stress in rivers is also of great importance. In this study, the boundary shear stress distribution in compound channels has been simulated with 2 numerical models of Fluent and Flow-3D software and compared with real experimental data (Wallingford, England), as well as a comparison between the output results of the shear stress distribution in the compound section is also performed based on the YLM method. To verify the accuracy of the simulation results, 3 methods of determining the convergence (error parameter) have been used to compare the computational results with the experimental results. The results showed that there was a very good match between the results of the numerical models and the experimental data, and as a result, both software could calculate the shear stress distribution appropriately. Generally, the numerical results of fluent software were closer to the experimental data compared to Flow 3D software.