By selecting the RNG k-ε model closed control equations,a three-dimensional mathematical model of the open-channel confluent flow is established based on the Flow-3D software,and the finite volume method is used for solving the equations.Three-dimensional numerical simulations are carried out for 45 combined working conditions composed of 9 confluence angles and 5 confluence ratios,and the characteristics of the flow structure in the confluence zone under different working conditions are analyzed.The results show that the flow characteristics in the open-channel confluence zone are complicated.The transverse velocity is the largest and has the widest distribution in the cross section with middle water depth.For large confluence angle and small confluence ratio,there is a negative velocity near the water surface and a secondary circulation flow is generated.With the decrease of the confluence angle or the confluence ratio,the influence of the branch channel flow on the main channel flow is reduced,and the non-uniformity of the vertical flow in the confluence zone becomes weaker.The maximum value of the transverse velocity in the main channel monotonically increases with the increase of the confluence angle or the decrease of the confluence ratio.When 60°≤α≤70°and Rq≈0.60,the influence of the transverse velocity on the flow structure in the confluence zone is relatively small.Furthermore,by analyzing the main and secondary areas’and isolation zones of the vertical velocity non-uniformity,the flow structure in the confluence area can be understood more intuitively.