Numerical Investigation of Bed Shear Stress and Roughness Coefficient Distribution in a Sharp Open Channel Bend

The helical flow leads to the redistribution of bed shear stress and roughness coefficient in open-channel bends, influencing transport sediment riverbed evolution process. To explore mechanisms underlying this redistribution, a 3D numerical simulation 180° sharp bend was performed by solving Reynolds-averaged Navier–Stokes (RANS) equations using Reynolds equation model (RSM) as anisotropic turbulence closure approach. results indicate that high zone appeared inner bank region from 50° 110° sections, section maximum gradually shifted outwards, owing advective momentum circulation cells. quantitative analyses terms depth-averaged Navier-Stokes contributions cross-stream cross-flow downstream were same order magnitude, overall contribution rate 20%. rates cross-flow, circulation, turbulence, pressure gradient transverse approximately 30%, 7%, 3%, 60%, respectively, indicating term arising water surface slope played dominant role. Chezy resistance showed an decreasing trend along bend. Therefore, effective expression considering streamwise variation centreline successfully established predict uneven distribution coefficient.