Author(s): Wei Cui; Huyong Huang; Wenxue Chen; Xiangpeng Mu; Zhe Liu; Lei Wang
Keywords: South-to-North Water Diversion Project; Radial gate; Calibration; Submerged flow; Free flow
Abstract: The Yanlinghe Gate is located in the Middle Route of the South-to-North Water Diversion Project, which is one of the largest water diversion projects in the world. It is a large scale radial gate with flat sills constructed on gently sloped channels. In this study, the hydraulic characteristics of the gate were analyzed and the formula for the discharge through the gate was calibrated based on approximately 18,000 datasets of measured sample data covering 17.1% to 97.6% of the gate’s design discharge. The research findings are as follows. The orifice flow is converted to weir flow when the bottom edge of the gate is about to disengage from the water surface (e/Hu=1). As the discharge increases, the Froude number of the vena contracta section under the gate decreases approximately exponentially from 0.985 to 0.152, and the flow transitions from supercritical flow to subcritical flow. The above described boundary exceeds the scope of the application of some traditional empirical formulas. Using the calibrated dimensionless formula, when the subsurface flow ratio is Xr < 0.95, the gate discharge calculation has a good accuracy with an error of ±10% and a maximum average error (MAE) of 2.26%. When Xr ≥ 0.95, the calculation error and the MAE reach 25% and 9.08%, respectively. In comparison, when an empirical formula with exponential discharge coefficients is used, the calculation error is reduced to within ±10% and the MAE decreases to 3.42% when Xr ≥ 0.95, demonstrating a significantly improved performance.