numerical simulation of overflow with effect of opening ratio gates on hydraulic of flow and jet trajectory

Nowadays the importance of reservoirs management makes the use of gates on the spillways crucial .This causes the change in hydraulic flow over the spillway and the aim of this study is to explore some of these hydraulic changes. In this research by using Flow-3D and volume of fluid (VOF method) and k-ε (RNG) turbulence model , chute spillway with ogee crest and flip bucket has been simulated. Additionally investigation on the effects of 4 openings 15%, 30%, 45% and 100% which is done by radial gates. has shown that the increscent of openings causes increscent velocity, depth and cavitation potential on spillways. Also in some openings with low discharge, due to the formation of low discharge which is lower than sweep discharge, formation of flow aggregated on the spillway is possible and the hydraulic effects of this phenomena should be should be taking into consideration. Also by simulation of jet trajectory from the flip bucket, Results showed low error in length and maximum height of the trajectory. In conclusion, using Flow-3D for prediction of tail water preservation is highly recommended. Eventually, two correlation for the dependency of length of the trajectory, maximum height, flow discharge and opening gate ratio were presented.