Research On The Fluid-solid Coupling Water Hammer And Its Vibration Characteristics Of The Pressure Pipe Of A Hydropower Station

The pressure piping is a very essential part in hydropower stations.Whether it can work safely is well connected to the normal operation of the hydropower stations.It is quite normal to see the valve opening or closing and when it is opening or closing the water hammer will show up.This extreme phenomenon can cause a great damage to the pipe system especially to the weak constraint formed pipe.There are many parameters that can bring effect to the water hammer such as the time spent on valve opening,the fluid velocity,the structure form of the pipe etc.Taking these factors into consideration is meaningful to the pipe design.Besides when there is water hammer inside the pipelines the FSI will exist along with it,how much effect it will bring to the results of water hammer is worth studying.At last,when the pipe has a vibration caused by the water hammer,it is quite meaningful to study it from both the time-domain and frequency-domain.Based on the aspect above,the main research work of this paper is as follow:(1)Starting with the classic water hammer calculation theory and FSI water hammer calculation theory,analyzing their differences and using them to calculate the water hammer effect of three different length of simple straight pipe basing on this two theory;Explaining the importance of FSI method to calculate water hammer and describing the influence degree of the FSI under different pipe length.(2)Based on a real pressure piping in a hydropower station,analyzing the influence caused by different valve closing time,different fluid velocity and different piers spacing.Using ADINA,a FEM software,to finish the numerical simulation.(3)From the aspect of Structure of Dynamics,describing the character of natural frequency and resonance of pressure piping.Calculating the natural frequency of the mode used in the front part.Analyzing the effect caused by different piers spacing to the natural frequency.(4)Using the Fourier transform to change the results in time-domain into frequency domain.Analyzing the vibration performance through the wave in frequency domain.Making a comparison between the natural frequency calculated by ADINA and the frequency-domain results transformed by Fourier transform to make sure the validity of the numerical method.