Majid Niazkar - PhD. Student, Civil and Environmental Engineering Dept., Engineering School, Shiraz University, Shiraz, Iran.
Seied Hosein Afzali - Assistant professor, Civil and Environmental Engineering Dept., Engineering School, Shiraz University, Shiraz, Iran. (Corresponding Author)

Circular weirs have been utilized as a flow-measuring device in open channel hydraulics. Since the corresponding theoretical equation for computing discharge is not adequately suited for practical purposes due to its complexity, empirical models are utilized as a preferable alternative. In this research, new improved simple formulas for semi-circular weirs with sharp and semi-circular crests were proposed in favor of achieving more accurate results. These relations were obtained using a new hybrid method for an experimental data base. The proposed correlations were compared with the ones in the current literature. The results demonstrates that the proposed models reduce the mean absolute relative errors, MARE, by 32 and 64 percentages.

Open channel flow measurement, Weirs, Semicircular opening, Sharp crest, Semicircular crest