Numerical Study on the Outer Bank Cell of Secondary Flow in a U-Shaped Open Channel

摘要

Due to the centrifugal force, a spiral flow is formed in a bend, presenting a rotating vortex in the vicinity of the inner bank and another rotating vortex in the opposite direction near the outer bank under certain hydraulic conditions, which have a significant effect on bank erosion processes. The renormalization group k-e turbulence model was employed to simulate the flows in a U-shaped open channel with various Froude number (Fr). The water level, vertical velocity and secondary flow structure were analysed. The outer bank cell (OBC) has a strong dependence on the Fr and the intensity of the OBC (Q_(OBC)) firstly increases and then decreases along the channel. The maximum Q_(OBC) gradually increases and the position of the maximum value first moves downstream and then upstream with the increasing Fr. At the apex of the bend, the nondimensionalize intensity of the OBC first decreases and then increases with the increasing Fr.