Study On Flow-induced Vibration Characteristics And Hydraulics Of Emergency Gate Of Dashixia Water Conservancy Project

The fluid-structure coupling of the emergency gate in the desilting tunnel during the closing process in moving water is perplexed.Its flow state of the gate area changes from full-flow to open-flow.Inappropriate support structure,improper bottom edge,unfavorable water flow conditions will all bring detrimental effects on its normal operation,and may cause a large vibration of the gate,even may cause a large amplitude of climbing phenomenon and endanger the safe operation of emergency gates.Therefore,it is very important to study the hydraulic mechanism of the emergency gate during the closing process in moving water.The factors make that large amplitude of climbing phenomenon are mainly the frictional force and the pulsating pressure of the water flow.And there is no definite conclusion.During the process of the falling,high head water flow on the gate will also cause huge down-suction force.And the exceeding the capacity of the hoist may cause an accident.Taking the emergency gate of the desilting tunnel in Dashixia project as the research project,the hydraulic characteristics of the emergency gate during the closing process were studied by physical model test and numerical simulation methods.The main results are as follows:(1)Due to test site restrictions,a new kind of test water supply arrangement is introduced.Using a pressureless water tank and a pressurized water tank to supply water for the test model.Using a relatively new experimental operation method,and laid the foundation for the smooth progress of subsequent experiments.(2)Based on the hydraulic test of the emergency gate of the desilting tunnel of Dashixia project during the closing process in moving water,the flow state and the characteristics of closed-door holding force under different working parameters of the accident gate during the closing process is studied.The effects of different operating conditions on the closed-door holding force are analyzed.It also optimizes the size of the gates with excessive closed-door holding force.Results shows: The maximum closed-door holding force during the falling process increases with the increase of the upstream water level and the opening degree of the downstream work gate.And there is no obvious correlation with the closing speed and opening area of the main beam.(3)Combined with EMD method.And based on the Dashixia physical model,the vibration of emergency gates with different upstream water levels,the opening degree of the downstream work gate,different landing speed,different opening area,different gate weights is explored.Results shows: the lower the upstream water level is,the lower the degree of the downstream work gate is,the lower the landing speed is,the vibration of the emergency gates caused by the pulsating pressure of the water flow becomes smaller.The opening of the main bottom beam can also reduce the vibration of the emergency gates.(4)The ANSYS was used to establish the finite element model of the accident gate,and the stiffness and strength were checked and the natural vibration characteristics were analyzed.The results show that the stiffness and strength of the accident gate meet the safety requirements.The dry and wet mode of the accident gate and the main frequency of the water flow pulsation are quite different,indicating that the possibility of resonance of the accident gate is small.