Flow-induced vibration of shell-type long-span gates. 1st Report. Fundamental vibration characteristics of the under-flow type.

Abstract

This study presents the fundamental characteristics for a flow-induced vibration of shell-type long-span gates which have a gate front consisting of vertical and inclined weir plates. The shell-type gates possess two freedoms to vibrate in the streamwise and vertical directions due to their bending flexibility. Both streamwise and vertical vibrations couple well with each other through hydrodynamical forces acting on the weir plates, thus resulting in a severe self-excited vibration. A two-dimensional model test for a shell-type long-span gate under small gate-openings was performed to measured the vibration frequency, the exciting ratio and the gate motion trajectories. From the obtained results, the fundamental characteristics, such as the vibration frequency ratios, a reduced fluid exciting coefficient, a reduced added mass, and a phase difference between the vertical and streamwise vibrations, were calculated. Furthermore, it was revealed from the measured gate motion trajectories that a press-shut device which causes a self-excited vibration is formed by a skillful dynamic mechanism of the coupled vibration.