# Characteristics of Plane Gate Vibration and Holding Force in Closing Process by Experiments
## 1 Introduction  
Vibration problems in water conservancy projects (including dams, gates and plants) caused by spillway is a common phenomenon. It can cause serious consequences and threaten the safe and stable operation of water conservancy projects [1; 2; 3; 4]. Flow-induced vibration of plane gate is an important subject in water conservancy engineering. Its vibration mechanism and vibration control method are both the focus of research. There are many excellent opinions in the literature dealing with the basic mechanism of flow-induced vibration of gate. [PERSON] [5] and [PERSON] [6], through the experiment, pointed out that the main cause of gate vibration was vortex formed by the failure of free shear layer at the bottom edge of gate. Based on the mechanism of flow-induced vibration, [PERSON] [7] divided the gate vibration into three categories: (1) gate vibration induced by the instability of water flow; (2) gate vibration induced by flow instability and structure feedback mechanism; and (3) gate vibration caused by the induced force generated by structure motion. [PERSON] [8; 9] believed that gate vibration was caused by the downstream vortex resonance. [PERSON] et al. [10; 11] supposed that fluid feedback force induced by gate vibration mainly included two aspects: pressure pulsation caused by the alternating flow andalternating excitation generated by the vortex at the gate bottom edge. [PERSON] et al. [12] considered that the vibration of radial gate with small opening was nonlinear self-excited vibration. In addition, [PERSON] et al. [13] and [PERSON] et al. [14] conducted studies on gate vibration from the perspective of frictional damping and gate opening-closing process in the physical model test. [PERSON] et al. [15] expounded the fluid inertia mode of the gate vertical vibration and believed that, in self-excited vibration process, variation of the effective flow area led to the flow pulsation and fluid inertia may aggravate the gate vibration. When gate vibrates by the hydrodynamic loads under the high-speed flow, flow field around the gate alters acutely and the structure dynamic loads change in turn, which forms the fluid-solid coupling effect. Most vibration control methods are to change the shape of the gate bottom edge, which could realize the stability of the flow pattern and weaken the vibration magnitude. For example, [PERSON] et al. [16] came up with a measure to effectively reduce hydrodynamic loads through placing penetrating orifice at the gate bottom beam. [PERSON] et al. [17] arranged some ventilation slots at the plane gate bottom and water could flow into the upstream panel and out at the gate bottom edge, which destroyed the reattachment effect between flow and gate bottom edge, smoothed the outflow state and effectively mitigate the vertical vibration. [PERSON] et al. [18] proposed a method that can effectively reduce the gate vibration magnitude and abate the gate fatigue damage by setting a guide plate at gate bottom edge. [PERSON] et al. [19] mounted the horizontal porous baffle at elevation below the free surface to reduce the vortex magnitude in the downstream and enhance the stability of plane gate. Due to the increasing demand for hydroelectric energy, construction of high-head water conservancy projects put forward a high requirement for the safe operation of gate. Much work so far has focused on the static load monitoring, vibration displacement, structural stress and so on. These achievements were largely obtained by fixed gate opening, and the flow under the gate can be viewed as a steady flow [20; 21; 22; 23]. However, little attention has been devoted to the gate vibration and its effect on the holding force in closing process. When gate is in continuously closing process, fluid boundary deforms in a large scale and the flow passing the gate becomes markedly unsteady process.