3D FSI Simulation of Flow-induced Radial Gate Vibration in a Dam Bottom Discharge Hole

Proper operation of bottom discharge holes is crucial for dam safety, but flow-induced vibration of outlet gate happens frequently because of high head, large discharge, complex flow patterns, or gate structure weakness. The violent gate vibration is normally called flow-induced gate vibration, even if physically the fluid-structure interaction (FSI) is obvious. In this study, taking a practical vibrating radial gate at the bottom discharge outlet as subject, we use FSI simulation to study the vibration mechanism and anti-vibration strategies. In this paper, the discharge hole and gate parameters together with the vibration phenomenon are first introduced. Then the FSI model built based on ANSYS-CFX is presented, which includes the bottom hole, radial gate, and downstream step and open channel. After that, the FSI simulation results are analyzed. The flow patterns and spatiotemporal distribution and spectrum of hydraulic fluctuation, together with the static and dynamic characteristics of the gate are investigated. By comparing hydraulic fluctuation and structure vibration characteristics, we found that the cavitation vortex behind the downstream step is the main sources of hydraulic fluctuation, which excites the gate and causes a resonance of fluid and structure. Based on this recognition, several air ventilation pipes under the step were added to eliminate cavitation vortex, and new simulations prove this is an effective means to reduce the gate vibration.