Abstract
The free water flow over a broad-crested weir with different down- and upstream inclinations was studied numerically using computational fluid dynamics software (FLOW-3D v11.0.4). Weirs of four various upstream and downstream configurations were investigated to determine the effect of weir shape on the produced coefficient of discharge (C<sub>d</sub>), upstream energy grade line (H<sub>1</sub>), and depth-averaged flow velocity using five different flow discharges. The obtained numerical results revealed that FLOW-3D program can be depended to simulate the flow over broad-crested weir adequately, as the differences between the numerical and experimental upstream head (h<sub>1</sub>) were in the range of 0.0 to 9.6%. Furthermore, reducing upstream slope played an essential role in increasing the discharge coefficient, and reducing the upstream energy grade line (i.e. static pressure above the crest), while downstream inclination showed a negligible influence. Generally, reducing the upstream slope by 50.0 and 70.5% increased discharge coefficient by 9.5 and 13.2%, while decreased the total energy grade line by 4.3 and 8.7%, respectively. According to flow velocity measurement, for the same upstream slope and discharge, the velocity resulted by the weir of inclined upstream and vertical downstream (BRV) was lower than that of the weir of vertical upstream and inclined downstream (VRB) by 28.0%.
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