Numerical Simulation of Flow-Induced Vibration on Gates With Underflow

Abstract

Flow-induced vibrations are an important issue in the design and operation of weir gates. Various mechanisms of vibration excitation are known. For underflow weir gates, the so-called press-shut mechanism is known to be a possible source of excitation. Hereby, the movement of the gate affects the flow regime in a way that a force is produced that acts in the direction of the gates movement. This self-excited process can lead to severe gate vibrations. Due to the coupled nature of self-excitation, it is insufficient to compare the distinct flow-induced forces and the natural frequency of the gate in a static model. A coupled approach is required in which both the flow and the gate movement are represented in a fully transient manner.Self-excited vibrations at hydraulic gates with underflow are often based on the coupling between vibration of the gate and the attributed flow-rate fluctuation. This phenomenon is referred as the press-shut mechanism. The investigation of self-excited vibrations requires the use of coupled models that reflect the transient flowregime and the motion of the body. A practical approach is developed which employs coupled numerical simulation to model the interaction between the vibrating gate and surrounding flow field. The energy that is transferred from the flow to the vibration is estimated as a value for vibration tendency. The method is applied to two practical examples of gates with underflow and verified with field measurements.