Analysis And Control Of Fluid-solid Coupling Vibration Characteristics Of Pipeline

Pipeline is used in all aspects of production and life,which is of great significance to people's high-quality production and life.Due to the lack of research and understanding of the vibration characteristics of the pipeline,it is very important to analyze the dynamic vibration characteristics of the pipeline and control the vibration effectively.Based on the fluid structure coupling theory and method,the vibration characteristics of straight pipes and bend pipes with different bending degrees are compared and studied,and the vibration control of straight pipes and bend pipes is studied respectively.The transient displacement and stress response of pipeline under certain pressure fluctuation are analyzed:(1)Based on the unidirectional fluid structure coupling,the prestressed modal analysis of straight pipe is carried out,and the influence of pipe wall thickness,pipe length,velocity and pressure on the natural frequency and vibration mode of straight pipe is studied.According to the results of modal analysis,the harmonic response of the prestressed pipe is analyzed,and the amplitude of each order is compared.Finally,the vibration control of straight pipe is analyzed.The results show that the thin-walled pipe is more likely to contract and vibrate.In practical application,the thickness of the pipe wall should be appropriately increased to improve the stability of the pipeline system;With the increase of pipe length,the natural frequency of straight pipe decreases a lot,which makes it easier to be excited to resonate;Under normal pressure and medium pressure,the influence of fluid structure coupling pressure on natural frequency of straight pipe conveying fluid can be neglected;The influence of fluid velocity on the natural frequency of pipeline is very small and can be ignored;The first and second-order oscillation amplitude of straight pipe conveying fluid is the largest,so it should be mainly controlled;In the process of the constraint moving from the inlet to the middle,the modal frequency increases in turn,and the frequency change speed is first fast,then slow and then fast.The results show that the restraint effect is the best in the middle of straight pipe.(2)Based on the unidirectional fluid structure coupling,the static analysis of fluid structure coupling was carried out for four kinds of elbows with curvature of ? / 4,? / 2,3 ?/ 4 and ?,respectively,in order to study the size and distribution of displacement and stress.The results show that the maximum deformation of the pipeline occurs on the inner side of the elbow,and the bending degree of the elbow has no effect on the static deformation distribution;The results show that the variation range and maximum stress of the outlet pipe wall are greater than those of the inlet pipe,while the variation range and maximum stressof the inlet pipe wall are greater than those of the bend;With the increase of bending degree,the maximum stress at the outlet decreases,and the position of the maximum stress at the outlet changes and moves from the inside of the pipe to the outside of the pipe.(3)Based on the unidirectional fluid structure coupling,the vibration characteristics of the elbow were analyzed.The results show that the bending pipe is more prone to swing vibration than the straight pipe.The swing vibration amplitude of the bend is the largest,and the maximum amplitude appears at the bend;The best vibration control effect is to set fixed restraint at the bend.When the fixed constraint cannot be applied to the bend,the bend can be constrained perpendicular to the symmetry plane of the bend.(4)Based on the two-way fluid structure coupling,the UDF program is compiled and the dynamic grid is used to analyze the vibration characteristics of the pipeline under certain sinusoidal pressure fluctuation.The results show that the maximum stress of the elbow occurs at the inner side of the pipe outlet,where fatigue failure is most likely to occur.The maximum stress of the straight pipe occurs at the outlet of the pipe,and the average vibration stress of the straight pipe is far less than that of the elbow.Among the straight pipes with the same length and different bends,the straight pipes have the best resistance to pressure fluctuation.The greater the bending,the better the resistance to pressure fluctuation.The research in this paper can provide a reference for further analysis of vibration characteristics and vibration control of straight pipes and elbows.