Simulation of Flow hydraulic in combined weir – gate structure by Flow3D

In Combined weir - gate structures, interaction of flow over weir and through gate brings up intense mixing and change bed shear stresses distribution. Hence, simulation of flow pattern in downstream of these structures is very complex. The object of this research is numerical modeling of combined flow over weirs and through gates by Flow3D software. Flow3D is a high accurate model in computational fluid dynamics for simulation of problem with complex geometry on wide limits of fluid flows in open channel hydraulic. By applying VOF method and RNG K-ε turbulent models, a series of simulation combined flow in weir - gate structure on rigid bed were performed and results were compared by some experimental data that carry out in this research. Results for the equation of Qup/Qin (equation 13) calculation error statistics software based on RMSE and R2 was evaluated and these values obtained 0.0994 and 0.992. Results of this research show that Flow3D with RNG K-ε turbulent model is appropriate to simulation of combined flow in weir - gate structure and estimation of free surface profile and discharge ratio passed over weir to under the gate.