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【Background】 Agricultural production in China uses approximately 70% of the total water consumed nationwide and developing sustainable irrigation districts faces many challenges such as channel leakage, inferior and dated irrigation projects, dwindling water supply and low water utilization efficiency. Optimal allocation of water resources is a key to developing water-saving irrigation, in which the Parshall flume has been widely used due to its high accuracy, convenient reading and ease of installation. In water conveyance, selection of a connection form in the flume controls the conveyance efficiency of the channel and its associated water resource allocation. 【Objective】 The purpose of this paper is to determine the optimal structure of the upstream inlet connection section of the Parshall flume, as well as the associated water pressure loss, water surface line, the measurement errors, velocity and pressure cloud under different inlet connections. 【Method】 We first used the SolidWorks software to design physical models of four inlet connection sections: interconnected arc transition, external arc transition, direct transition. The control was without transition. The ANSYS18.0 software was then used to generate the meshes and simulate water flow for each design. The simulated data were analyzed using the Tecplot and Origin software. 【Result】 The filament line in the Parshall flume was smoother with an inlet connection than without one. The local waterhead loss in the flume was the highest in transition without connection section and the lowest in the inner circular transition section. The relative errors of the flow measured by the flume decreased with incoming water flow rate, and when the incoming flow rate was 0.01 m3/s, the errors of the above four designs were 16.3, 15.9, 15.4 and 17.7 respectively. When the incoming flow rate increased to 0.2 m3/s, the errors of the above four designs reduced to 6, 5.9, 5.2 and 5.5 respectively. Among the four designs, the rectilinear transition section was most accurate. The change in velocity gradient and pressure cloud in the longitudinal profile of the flume was noticeable, and the highest velocity and water pressure were in the throat section and the upstream hydrosphere, respectively. The largest turbulent kinetic cloud map was in the region of the gas phase distribution, and the gas phase was more fluidic than the liquid phase. The energy exchange between molecules is more intense and consumes internal energy. 【Conclusion】 The flume is more accurate when the incoming flow rate is high. Adding an inlet connection section can reduce the measurement errors induced by flume deformation caused by water pressure. |
