Numerical Study of Flow Characteristics Over Pivot Weirs

Pivot weirs have a lifting mechanism to change the weir angle relative to the channel bed. These are installed across the waterways in the form of multiple weirs in a row. The water level will be adjusted by changing the weir angle. In this study, the flow over the pivot weirs was simulated with different flow discharges and angles using Ansys CFX model to investigate the flow characteristics. The model was evaluated using USBR experimental data. The standard K-ε turbulence model was considered as the best model for numerical analysis. According to the results, discharge coefficient increases with the inclination angle up to 1.076. The results showed a slight difference in comparison with the previous studies where values of 1.121, 1.110 and 1.082 were presented. The discharge coefficient equations were developed for the weirs. The equations for various hydraulic parameters, including upstream water depth, water head on the crest, the ratio of water head over the crest to the weir height, and weir angle were developed. Based on the developed equations, the operation of the weirs was analyzed during flood events.