Numerical analysis of flow hydraulics in a culvert-weir system with a circu-lar crest and gate

Weirs are essential components in water engineering projects, effectively managing surface flows. Among these structures, circular-crested weirs are particularly popular due to their simple design and high flow capacity. This study primarily focuses on investigating the hydraulic characteristics of flow in a culvert-weir system with a circular crest and analyzing the effects of critical parameters such as crest radius and gate opening on the discharge coefficient. For this purpose, velocity profiles, water surface levels, and other flow parameters were analyzed as the main variables. Various models of the culvert-weir system with circular crests were designed and meshed using Gambit software, then imported to Fluent software for detailed computational fluid dynamics (CFD) simulations. The discharge coefficients of the weir crest, gate, and the entire structure were calculated and compared under different water load conditions and independent parameters. The results indicate that the discharge coefficient of the weir crest is higher when a gate is present compared to a gate-free condition. Furthermore, the discharge coefficient increases as the crest radius decreases and the gate opening expands. Additionally, the comparison between numerical simulation results and reliable experimental data shows a high level of accuracy and satisfactory agreement, validating the numerical modeling approach. This study provides precise data and practical analyses to improve the design and performance of combined hydraulic structures.