Self-Excitated Oscillations of a Floating Gate Related to the Gate DischargeCharacteristics

摘要

The large amplitude oscillation that was observed in a scale model of a 360 mwide storm-surge barrier with two floating sector gates, was found to be coupled to transverse (standing-wave) water level oscillations in the downstream (river side) reach. A simplified theoretical model was conceived in which the down-stream reach at each of the gates was replaced by a(n) (enclosed) basin with a free water surface, connected by a conduit to water outside the basin. The basin/conduit system has a resonance frequency equal to the standing long wave. The feeding discharge of the basin (underneath the gate) was supposed to have a linear relation to the water-level variation in the basin. It is shown that if the ratio of these two elements is positive, a self-excitation of the basin may occur; otherwise the oscillation damps out. This criterion for self-excitation has probably a more general applicability.