Numerical Investigation on the Impact of Conduit Curvature of the Bottom Outlet Service Gates on the Hydraulics of Flow

Bottom outlets are used as lateral hydraulic structures in dams for flood control, sediment discharge, and flow transition. In this study, numerical simulation of flow in the bottom outlet including slope, various geometrical sections, and conduit curvature in front of the service gate were investigated by using FLOW-3D as a computational fluid dynamic (CFD) model. To solve super-critical flow, k-ε model, a turbulence model was also used. Objectives of this study are: proposing an appropriate geometric structure of flow conduit to eliminate downstream turbulent flow pattern and predicting conduit geometric change impact on flow characteristics at the gate section and downstream of the structure. Results from numerical modeling were compared with experimental ones. Results indicated that by choosing a direct length of 25 meters in front of the gates, values of turbulent energy and flow pressure had decreased 27.86% and 26.17% before and after the gate, respectively. Furthermore, significant difference was not observed by using longer distances in front of the gate.