| Nowadays,pressure pipes are widely used in various projects.In many water conservancy projects,pressure pipe is extremely important water conveyance structures.The safe operation of pressure pipe system directly affects the production of hydropower station.The vibration of pressure pipe system is closely related to its design and operation.Therefore,it is very important to master the vibration characteristics of pressure pipe correctly and timely.On the basis of Structural Dynamics,Potential Flow theory,Hydraulics and Fluid Structure Coupling theory,this paper simulates the natural vibration characteristics and dynamic response of pressure pipe under sustained harmonic external excitation by using ADINA finite element analysis method.Research on the response of pressure pipe in this paper may provide some reference for the safe operation of pipeline system in the future.The main work of this paper is as follows:1.In the research,physical model was designed.Arrangement and facilities of pressure pipes which supply water in hydropower stations and pump stations,as well as the quick opening and closing of valves or guide vanes,the transient transition process of water flow and pipes are simulated in this model.Fluctuating pressure,the amplitude and duration curve of pipeline vibration are measured.Characteristics of them are summarized in this paper.Comparative data for the subsequent numerical simulation analysis of the dynamic response of the pressure pipeline are provided through this.2.Moreover,pressure pipe model and fluid model(potential fluid)are built in the structure module of finite element software ADINA.The fluid structure coupling mode and the natural frequency and mode shape of the pressure pipe system are obtained.The influence of different pipe diameter and pipe wall thickness on the natural vibration characteristics of pipe structure is further studied on the basis of simplified pipe system.This is the starting point for further transient dynamic analysis of pipes.3.On the basis of the above preparations,a three-dimensional transient dynamic analysis model of the pressure pipe system is established by using the finite elementsoftware ADINA.Dynamic characteristics of the pipeline structure under continuous harmonic external excitation with different amplitudes and frequencies are simulated in this model.Research on dynamic response of the pipeline structure after resonance is the key points.The final results show that in the safety design of real engineering project,the pipe structure is not affected by the high-order resonance,but the first-order natural frequency of the pipeline system should be avoided.It can be seen from the physical model test and numerical simulation that the finite element method can effectively help to avoid the adverse factors in design and construction of real engineering project.At the same time,this study may also provides some reference for the design of pressure pipe system and the improvement of safety and reliability of the engineering project. |
