Salma Ajeel Fenjan; Ali Akbar Akhtari; Mohammad Hadi Tavana
Abstract
In this study, the performance of vertical and tilted crown weirs with different angles of the weir crest across the flow has been investigated using numerical and experimental models. Accordingly, various experiments are conducted on tilted crown sharp-crested weirs under different free-flow conditions. ...
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In this study, the performance of vertical and tilted crown weirs with different angles of the weir crest across the flow has been investigated using numerical and experimental models. Accordingly, various experiments are conducted on tilted crown sharp-crested weirs under different free-flow conditions. Moreover, computational fluid dynamic (CFD) modeling has been done using Fluent software to determine the best form of the discharge coefficient (Cd). In this study, the RNG model is used to define turbulence in the fluid flow and the two-phase volume of fluid (VOF) method is applied to define the interface of water-air in the flume. To verify the accuracy of the CFD model, the experimental data that was done in this research are used. Moreover, another goal of this research is to investigate the influence of the different angles of weir on hydraulic characteristics of flow such as pressure, velocity and Cd parameters. The results show that by increasing the weir crest angle across the flow (α), the Cd values are almost constant. Furthermore, the numerical results are in good agreement with the experimental models. As, the comparison of numerical and experimental data shows that the maximum absolute relative error (ARE) obtained are 2.8 %, which indicates the high accuracy of the CFD model. The vortex area with return velocity vectors can be seen in downstream of the weir and these vectors increase near the weir. In all velocity values, by decreasing the angle of weir to the flow direction, the Cd values increased and tends to a constant value while, the pressure values decreased. As for the velocity values in ranges of 0.05-0.23 m/s, the Cd value is ranged in 0.64-0.675. Finally, as the Reynolds and Froude number increase, the discharge coefficient decreases and tends to a constant number of 0.65 approximately.
Akbar Safarzadeh; Babak Khaiatrostami
Abstract
Water supply from rivers is accomplished with flow diversion through an intake structure. A lateral intake like bifurcation is the simplest method to withdraw water. However, flow at a channel bifurcation is turbulent, highly three-dimensional (3D) and so has many complex features. This paper reports ...
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Water supply from rivers is accomplished with flow diversion through an intake structure. A lateral intake like bifurcation is the simplest method to withdraw water. However, flow at a channel bifurcation is turbulent, highly three-dimensional (3D) and so has many complex features. This paper reports a 3D numerical investigation of these features in an open channel flow. Simulations have been done on rectangular channel geometry, with smooth bed and sidewalls. The standard k-ɛ, k-ω model of the Wilcox, and RSM turbulence models are compared using the commercial code FLUENT. The simulation results have been compared with available experimental data. It was found that all of the turbulence models tested here accurately predicted velocity profiles in the main channel but in the branch channel, the RSM model with the k-ω model performing better than the k-ɛ model. Predicted flow physics are in close agreement with previously reported experimental results.
