3d Modelling of Hydraulic Characteristics Of the Compound Curved Channel

Abstract

During the evolution of a meandering river, the outer bank is consistently eroded, frequently resulting in bank collapse, which raises significant concerns about the stability of the riverbank. This study utilizes the Reynolds Stress Model (RSM) in Ansys-Fluent suite to simulate the hydrodynamics of a compound curved channel with shoals located at the inner bank, studying the influence of secondary flow on the distribution of shear stress, specifically on the outer bank, and its subsequent effect on bank erosion. Additionally, the distribution of friction factor in the compound curved channel has been calculated based on flow velocity and shear stress numerical simulations. The results from the RSM demonstrate that the maximum intensity of secondary flow occurs at the exit of the bend; Under the influence of secondary flow, the maximum shear stress on the outer bank at the bend increases significantly, reaching 1.2 times the average shear stress, compared to approximately 1.05 times in the straight sections; The location of the maximum shear stresses on the outer bank corresponds with the centre of the outer bank circulation of the secondary flow, and those maximum shear stresses prove to be a more accurate indicator of erosion rates compared to the average shear stresses; Moreover, the cross-sectional average friction factor in the majority of the bend is greater than that of the straight section, with the maximum average friction factor in the bend reaching 2.6 times that of the straight section. In the same cross-section, zonal evaluation of the friction factor in bend can more effectively predict the distribution of depth-averaged velocity, particularly in regions near the bank.

Keywords: compound curved channel, 3D modelling, secondary flow, bed shear stress, bank erosion, friction factor