Optimization Study of Valve Closing Schemes for Long‐Distance Gravity Flow Water Supply Systems Based on the NSGA ‐ II Algorithm

To address safety hazards caused by valve‐closing water hammer in long‐distance gravity flow water conveyance projects and ensure the safe and stable operation of water transmission networks. This study focuses on the Ruyang Water Supply Project of the Northern Trunk Pipeline of Qianping Reservoir in Henan Province (the water conveyance pipeline has a total length of 87.4 km and a water level difference of 102 m). Using Bentley Hammer software to construct a hydraulic calculation model, the water hammer effects of different valve closure schemes were simulated and analyzed based on the characteristic line method. Combined with NSGA‐II, this study investigates valve closure scheme optimization. The research first analyzes the influence patterns of three one‐stage valve closure durations—10, 20, and 60 s—on water hammer effects. Subsequently, optimization calculations were performed for the stage‐two and stage‐three valve‐closing curve schemes, with the system comparing the water hammer protection effectiveness of different valve‐closing modes; the multistage valve‐closing scheme was further optimized using the NSGA‐II algorithm, validating the reliability and superiority of the optimized solution. Research findings indicate that valve closure time is negatively correlated with the intensity of water hammer effects. The shorter the valve closure time, the more pronounced the water hammer effect. The multistage valve closure optimization scheme demonstrates significantly superior protective performance compared to the single‐stage closure scheme. The three‐stage valve‐closing scheme optimized using the NSGA‐II algorithm not only achieves a higher optimization success rate but also provides more effective protection against water hammer. The optimization results are highly dependent on the selected hydraulic model, boundary conditions, valve closure duration constraints, objective function, and parameter ranges; in practical applications, they must be re‐validated based on specific engineering conditions.