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Abstract
Practical trapezoidal cross-section weirs are pretty commonly used in countries with developed agriculture to take water or discharge floods for irrigation systems with medium and low water heads. The weir shape with a square trapezoidal cross-section with downstream slopes is widely applied, with the advantage of ensuring the ability to discharge floods and conveniently connect the flow with the downstream works. However, research and published data based on theory and experimentation for this type of dam are still limited and incomplete. The data used to calculate and determine the discharge capacity of the spillway (Cd) in the design work needs to be looked up and interpolated into a small data set from standards or hydraulic calculation manuals. Therefore, to supplement and complete the data set to determine the discharge coefficient, this paper applied the Flow-3D model to study the flow over the spillway, build the curves of the relationship between the discharge coefficient and the geometric characteristics of the spillway, and simultaneously, the study used a combination of statistical methods to establish quantitative expressions of the discharge coefficient according to the geometric characteristics of the weir and the flow conditions with high correlation coefficients, the research results have small errors compared to existing specialized documents. In addition, the research results are a helpful reference document on the hydraulics of flood drainage works.