Numerical Investigating of Flow and Discharge Coefficient Over the Duckbill and Oblique Weirs

For a given channel width, duckbill and oblique weirs have longer effective length, and this could be effective on their dis-charge coefficients and efficiency. In this study, we tried to examine the role of some of the hydraulic and geometric parameters of mentioned weirs and their height on the discharge coefficient into the channel using the Fluent numerical model and the results of this model compared with the Flow-3D model and experiments data. The pressure, velocity, turbulence, and the free surface of the flow were modeled by k-ε RNG and volume of fluid (VOF) algorithms, respectively. The NRMSE of the Flu-ent model in the simulation of the discharge coefficient was 0.0565, which indicates the high accuracy of the model. Results showed that in both weirs, the discharge coefficient decreases with increasing discharge or upstream head. The maximum dis-charge coefficient was found in the H/P≤ 0.35 in both weirs. The results indicated the oblique weirs had a higher discharge coefficient compared with duckbill weirs and thus had higher flow capacity.