627 フォルソンダム・テンタゲートの大開度放水時における複合発散振動に関するモデル実験

Abstract

This paper presents the model test results of coupled-mode self-excited vibration of Folsom dam Tainter-gate at its large openings. The Folsom gate was represented by a 1/31-scaled model, where the whole gate vibrates around the trunnion pin and the skinplate vibrates in the streamwise direction. Both the vibration modes couple well through hydrodynamic and inertial forces. This type of coupled-mode vibration is accompanied by the flow-rate variation under the gate, and under certain conditions a violent self-excited vibration is induced. In the present model tests, the Froude number was fixed at 6.67, the reduced gate opening height relative to the gate submergence depth was adjusted up to 11.9%, and the whole gate vibration frequency was varied. As a result, it was concluded that the gate dynamic instability decreases in its intensity, with increasing the gate opening, and the fluid excitation effect disappears at the reduced gate opening of about 14%.