Study On Dynamic Characteristics Of Powerhouse Structure Of Bulb Tubular Turbine Hydropower Station Based On Fluid-Structure Interaction

The bulb tubular turbine hydropower station is the most suitable way to develop low-head hydraulic resources,generally located in river channel.As the advantages of its high hydraulic efficiency,a larger unit discharge and a higher unit speed,less civil engineering and smaller investment,the bulb tubular turbine hydropower station has been widely used in the practical engineering at home and abroad.The powerhouse of bulb turbine hydropower station is a water-retaining powerhouse and powerhouse structure is an important part of water-retaining buildings,and it has a big size of unit flow channel,the interaction between water and structure has a great influence on some structural characteristics of powerhouse.During the operation of hydropower station,the dynamic characteristics of powerhouse structure under the action of seismic load and fluctuating pressure load has always been the focus of its study.So the natural vibration characteristics and dynamic response of powerhouse of an actual bulb hydropower station is studied based on fluid-structure interaction in this thesis.And the main research contents are as follows:(1)The three-dimensional coupling FEM model of powerhouse-foundation-water is established to study the influence of water on the natural vibration characteristics of powerhouse structure.The results indicate that the frequency value of powerhouse is reduced considering the action of water,the value achieved by additional mass method is slightly smaller than the value achieved by the fluid-structure interaction method,and the vibration modes of these methods are also changed.The water influence should be taken into account in the resonance vibration checking of powerhouse and there has no big difference with additional mass method and fluid-structure interaction method.(2)The hydrodynamic pressure of the flow channel caused by earthquake is studied based on fluid-structure interaction method,which indicates that the hydrodynamic pressure in the upstream flow channel is larger than that of the downstream draft tube.And compared with the dynamic response of powerhouse structure under the three schemes of no water,using additional mass method to consider effect of water and using fluid-structure interaction method to consider water,it is found that two methods of considering water both increase the dynamic response of most parts of powerhouse,and the increase amplitude of additional mass method is larger than that of fluid-structure interaction method.The results of displacement and stress response accord with this rule more obviously,the results of velocity and acceleration response do not accord with it obviously.So the influence of water on velocity and acceleration of powerhouse structure is much more complex,the action of water should be considered reasonably in seismic analysis of powerhouse structure.(3)The difference of vibration response of powerhouse under different unit output condition of the same design head is studied by using time history analysis method,based on the fluctuating pressure of flow channel calculated by CFD.The results indicate that the fluctuating pressure of whole flow channel is increased with the decrease of unit output,and the vibration amplitude,velocity and acceleration is also increased,less than the recommended value of vibration standard of the powerhouse.The frequency of runner blade is the main frequency of causing the vibration of powerhouse.(4)The difference of vibration response of powerhouse between using harmonic response analysis method to partition loading and using time history analysis method is studied under the maximum unit output condition.The results indicate that the root mean square value of vibration amplitude,velocity and acceleration of auxiliary powerhouse floor achieved by harmonic response analysis method is larger than that of time history analysis method,and it is found that the fluctuating pressure of region between guide vane and runner and draft tube region play the most role in the vibration of powerhouse when used harmonic response analysis method to calculate its vibration.