Improving the Performance of the Weir-Orifice Structure by Changing the Weir Angle by Using Flow-3D Model

In this research, the weir-orifice composite structure was simulated using two water elevations and six analyzes in the Flow-3D model, and the results were validated with laboratory data. Three grid groups were used to select the optimal block mesh. However, the K-Ɛ and RNG turbulence models were used to select the appropriate turbulence model. The block mesh with 198750 cells was selected as the most suitable mesh for this simulation. The results showed that the RNG turbulence model with the correlation coefficient of 0.92 has the highest accuracy and speed. The numerical model investigated the velocity, pressure, water level profile, and flow lines, and the results were presented. Then, by using three water heights of 0.0756, 0.0973, and 0.1243 m and applying ten different angles at each height, by changing the location of the overflow from horizontal to diagonal in the cross-section of the circular channel, changes in the discharge coefficient of the case were investigated. Also showed that the diagonal weir had increased the discharge coefficient. The lowest and highest discharge coefficient values were obtained for angles of 2.5 and 12.5 degrees with values ​​of 0.67 and 0.84, respectively. Weir with an angle of 12.5 degrees with an increase of 13.27% of the discharge coefficient has the most increase in this coefficient among the applied angles.