Investigation Discharge Coefficient and Stage-discharge Equation for Broad-Crested Weirs Including the Effects of Sloping Crest and Upstream and Downstream ramps

Document Type : Research Article


1 Associate Professor, University of Tabriz / Department of Water Engineering

2 Ph.D Candidate, University of Tabriz / Department of Water Engineering


Weirs are one of the types of hydraulic structures in water projects that with different cross section have been widely used as flow measuring, controlling and regulating of upstream water surface for turnouts devices, in conveyance water canals or body of dams. In this study, the hydraulic characteristics of flow over broad-crested weirs including the effects of different configurations of sloping crest and upstream and downstream ramps using of finite volume method (FVM) by the ANSYS FLUENT software was investigated. Numerical simulations were validated by experimental results. The results showed that discharge coefficient (Cd) for the BCW-UR-PSC and BCW-UDR-NSC weirs are higher than the BCW-UDR-HC weir. The average increase of Cd in BCW-UDR-NSC respect to BCW-UDR-HC in such a way that θ=-4.76° and- 9.46° is 18% and 25%, while the average increase of Cd in the BCW-UDR-PSC respect to the BCW-UDR-HC for same condition (θ=+4.76° and+9.46°) is 10% and 18%. It was found that both of the BCW-UDR-NSC and BCW-UDR-PSC, the Cd increases with steeper of the crest slope (or increasing θ). Also, the results showed that for BCW-UDR-PSC, value of Cd is 0.35≤Cd≤.47, however for the BCW-UDR-NSC, values of Cd are between 0.42≤Cd≤0.48. This shows that the Cd is affected by the sloping of the crest in such a way that negative slope respect positive slope has more impact in this increase. The average increase of the Cd in BCW-UDR-NSC respect to the BCW-UDR-PSC is approximately 8%.


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