كليدواژه :
سرريز خط جرياني , تبديل ژوكوفسكي , نرمافزار OpenFoam , نيمرخ سرعت , توزيع فشار
چكيده لاتين :
The present study is subjected to analytical, numerical, and experimental simulation of hydraulic characteristics of flow over the streamlined weirs. Numerical simulations were performed using an open source software namely OpenFoam. According to the objectives of the present study, to evaluate the results of numerical modeling, experimental investigation was conducted, studying different models of streamlined weirs, experimentally. The profiles of the experimental models as well as the simulated numerical models were designed based on the Joukowsky transform function. By analyzing the results of different turbulence models including standard k-ε model, realized k-ε model, RNG k-ε model, k-ω SST model and Reynolds stress LRR model, the k-ω SST model was chosen as the most accurate numerical turbulence model for the simulation of flow over the streamlined weirs. The results of the numerical simulations for different flow discharges and different geometrical characteristics, indicated that, increasing the flow discharge and the relative eccentricity in Joukowsky transform function, tends to increase the velocity and consequently decrease the pressure over the weir crest. Therefore, the lowest pressure and the most probable potential of cavitation belongs to the circular-crested weirs with λ = 1 and high flow discharges. Furthermore, the results show that the greatest bed shear stresses and the compressive forces occur at the downstream end of the circular-crested weirs, thus the downstream zone of the circular-crested weirs is responsible to large values of bed erosion. This is partly due to formation of shock waves, reduction of the flow depth and enhanced velocity of flow downstream of the circular-crested weirs. Furthermore, the lowest bed shear stresses occur at the upstream end of the circular-crested weirs. Therefore, potential of sedimentation upstream of the circular-crested weirs increases. Accordingly, by employing streamlined weirs with λ< 1, and an appropriate curvature, unfavorable flow conditions would be improved, leading to a more safe and economic hydraulic structure. The present study is subjected to analytical, numerical, and experimental simulation of hydraulic characteristics of flow over the streamlined weirs. Numerical simulations were performed using an open source software namely OpenFoam. According to the objectives of the present study, to evaluate the results of numerical modeling, experimental investigation was conducted, studying different models of streamlined weirs, experimentally. The profiles of the experimental models as well as the simulated numerical models were designed based on the Joukowsky transform function. By analyzing the results of different turbulence models including standard k-ε model, realized k-ε model, RNG k-ε model, k-ω SST model and Reynolds stress LRR model, the k-ω SST model was chosen as the most accurate numerical turbulence model for the simulation of flow over the streamlined weirs. The results of the numerical simulations for different flow discharges and different geometrical characteristics, indicated that, increasing the flow discharge and the relative eccentricity in Joukowsky transform function, tends to increase the velocity and consequently decrease the pressure over the weir crest. Therefore, the lowest pressure and the most probable potential of cavitation belongs to the circular-crested weirs with λ = 1 and high flow discharges. Furthermore, the results show that the greatest bed shear stresses and the compressive forces occur at the downstream end of the circular-crested weirs, thus the downstream zone of the circular-crested weirs is responsible to large values of bed erosion. This is partly due to formation of shock waves, reduction of the flow depth and enhanced velocity of flow downstream of the circular-crested weirs. Furthermore, the lowest bed shear stresses occur at the upstream end of the circular-crested weirs. Therefore, potential of sedimentation upstream of the circular-crested weirs increases. Accordingly, by employing streamlined weirs with λ< 1, and an appropriate curvature, unfavorable flow conditions would be improved, leading to a more safe and economic hydraulic structure.
