عنوان مقاله [English]
In recent years, as dam safety standards have increased, hydraulic engineers have become more eager to design an economical and safe energy dissipation system at the main flood evacuation course. Ogee spillway and flip bucket are the most used types of spillway and energy dissipation structures. The main aims of the present research were modeling and analyzing hydraulic characteristics of the flow over convergent chute and flip bucket with negative slope of Gelvard Dam, Neka, the north of Iran using Flow-3D software and comparing the results of spillway geometry modification in relation to the initial model. The validation results of numerical model with the experimental data showed that RNG model is the most appropriate turbulence model. Moreover, with respect to the dimensions of computational cells, sensitivity analysis showed that square mesh with dimensions of 0.6 m is appropriate. Considering the results of the numerical modeling, due to increasing the flow velocity more than 20 m/s at the end of chute and maximum pressure of -70000 pa in this area, cavitation threatens the circular arc. Therefore, the slope of the chute and circular arc radius was changed respectively and numerical analysis results were remeasured. The results showed that by reducing the chute slope, the critical points of cavitation decreased from 3 points to 1 point. In addition, it was indicated that changing circular arc radius had no considerable effect on hydraulic characteristics. It just showed that when arc radius increases, jet length increases up to 5 m.