Numerical Simulation Study on Orifice-Combined Overflow Fishway in Nimumaqu River

JIANG Yunpeng; QIAO Yu; LIU Xinjing

doi:10.3969/j.issn.1004-7328.2026.增刊1.027

Abstract：Taking the orifice-combined overflow fishway in Nimaumaqu River as the research object,this paper constructs a proportional three-dimensional numerical model based on the FLOW-3D platform to carry out refined hydraulic characteristic simulation,aiming to reveal the internal flow patterns,evaluate the rationality of design,and provide support for engineering optimization and operation and maintenance.The computational domain has a total length of 63 m,with a rectangular channel net width of 1.5 m,and a longitudinal slope of 5.7%.A total of 38 centrally arranged single circular orifice baffles are arranged with a spacing of 1.5 m and a hole diameter of 0.25 m.A structured grid with a cell size of 0.06 m is adopted,resulting in a total of 1.76 million elements,and the grid independence is verified to ensure reliability.The Reynolds-averaged Navier-Stokes equations are selected and boundary conditions are set based on normal hydrology for steady-state simulation.Through post-processing,parameters such as flow pattern,flow velocity,and turbulent kinetic energy are extracted,and their spatial distribution patterns are analyzed,with the influence of key parameters of the fishway being identified and evaluated.The results indicate that the design parameter s of the fishway are reasonably matched,with stable internal flow patterns and uniform flow velocity and water depth distribution.The hydraulic environment is suitable for the migration of indigenous small fish species,with only weak eddies exist at baffle corners,which may be slightly optimized.The research findings can provide data support for the implementation of this fishway project and references for the design and simulation of similar river fishways.