Study of variations in discharge coefficients for broad-crested weirs with sloped upstream and downstream faces using numerical simulation

Document Type : Research Article


Department of Water Engineering, Faculty of Agriculture, University of Tabriz


Weirs are structures that are important for measuring flow and controlling water levels. Previous studies have shown that the discharge coefficient is not constant and depends on the weir crest length, the height of weir, the upstream head, and the weir upstream and downstream slopes. In this study, the effect of these parameters on the discharge coefficients (Cd) are investigated by numerical simulation. Results showed that the downstream face slope has little effect on Cd. For 0.1<H1/w<0.4 by decreasing the upstream slope, Cd increases, where H1 is the water head on the weir crest and w is the length of the crest. Also, for the same range, by decreasing the height of the weir (p), the Cd increases. For 0.16<H1/p<2, as the length of the crest decreases, the Cd increases. By comparing the numerical simulation results to physical measurements, determination coefficient (R2) was between 0.71-0.86. In addition to Cd, extraction of other more detailed information such as water level profiles and velocity profiles at different locations are provided and comparison with other studies was carried out.


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