Saeed farzin - Assistant professor, Department of civil engineering, Semnan university, Semnam, Iran
Elham zamiri - M.S. student, Department of civil engineering, Semnan university, Semnam, Iran
Hojat karami - Assistant professor, Department of civil engineering, Semnan university, Semnam, Iran
Shahab nayyer - M.S. student, Department of civil engineering, Semnan university, Semnam, Iran

Cylindrical weir is one of the hydraulic structures model that due to simple design, ease of floaters passage and sustainable pattern of flow is widely applied. In this article, flow over the cylindrical weir with 7.5 (cm) diameter on flume by 6 (m) length was modelled in Flow-3D software as three-dimensional and the results were compared with the physical model, also the results of three turbulence models LES, RNG and k-Ɛ were compared and it was found that the results of K-, turbulence model best fit the results of the physical model. Root Mean square Error of comparing the numerical discharge coefficient with physical quantities was obtained 0.3427, which represents a good agreement hydraulic characteristics obtained from numerical and physical model, it was also observed, cylindrical weir discharge coefficient values is greater than 1.

Discharge coefficient, cylindrical weir modelling, Flow-3D, k-, Turbulence model