Experimental and numerical analysis of flow over a rectangular full-width sharp-crested weir

Abstract

Weirs are a type of hydraulic structure, used for water level adjustment, flow measurement, and diversion of water in irrigation systems. In this study, experiments were conducted on sharp-crested weirs under free-flow conditions and an optimization method was used to determine the best form of the discharge coefficient equation based on the coefficient of determination (R2) and root mean square error (RMSE). The ability of the numerical method to simulate the flow over the weir was also investigated using Fluent software. Results showed that, with an increase of the ratio of the head over the weir crest to the weir height (h/P), the discharge coefficient decreased nonlinearly and reached a constant value of 0.7 for h/P > 0.6. The best form of the discharge coefficient equation predicted the discharge coefficient well and percent errors were within a ±5% error limit. Numerical results of the discharge coefficient showed strong agreement with the experimental data. Variation of the discharge coefficient with Reynolds numbers showed that the discharge coefficient reached a constant value of 0.7 when h/P > 0.6 and Re > 20000. Keywords: Discharge coefficient, Measurement, Numerical model, Sharp-crested weir, Weir height