Discharge Coefficient of Duckbill Weir by Using Side Gate Structures in Irrigation Networks

Due to extensively used of duckbill weirs in irrigation networks the study of these structures is very important. In this study flow pattern and discharge coefficient of duckbill weir have been studied when the gates are installed in both front and side wall of the weir. The Flow-3D software has been also used for simulation of flow pattern. The velocity measurement have been used for calibrating the model. The results show that the flow capacity of weir can be increased by 14% when the gates are used in side wall of the weir. The results also showed that by diverting some part of flow from side gates, the sediment can transfer to downstream. The results showed that variation of discharge coefficient of weir is more affected by gate opening rather than the gate length. Comparison of numerical and laboratory data shows that the Flow-3D software can simulate water surface profile and flow pattern with high accuracy. The maximum relatived error for simulation of water surface profile and longitudinal velocity is 2.09 and 1.33 respectively.