Research On Resonance Characteristics Of The Fluid-conveying Pipe During Water Hammer

As one common fluid-conveying structure,pipes play an important role in many industrial fields.The vibration of fluid-conveying piping system is one kind of hydraulic phenomenon produced by the coupling effect between the pulsating flow and the solid pipe,which will not only lead to the noise damage,but also cause damage to the pipeline system.There is no denying that this damage will threaten the safe operation in the pipeline system.As one type of extreme hydraulic phenomenon,water hammer resulting in the vibration of the pipe is often caused by the sudden change of the boundary conditions in the pipeline.Therefore,the research about the vibration characteristics about water hammer in the liquid-filled pipe is great significance and economic value of the engineering.According to the unsteady flow in the pipeline system,the numerical method and resonance characteristics of the vibration induced by the water hammer in the pipeline system are analyzed in this paper.The research work involves several aspects as follows:Based on the fluid-structure interaction four-equation,the split-coefficient matrix method is introduced.The axial vibration model of the pipeline is established by the split of the coefficient matrix and the diagonalization of the matrix.And the finite difference method and implicit difference method are spatial and temporal discretizations for governing equations.The accuracy of the proposed numerical model is verified by comparing the present results with MOC prediction in the past.In this paper,the process of water hammer is simulated by controlling the nonlinear variation of flow velocity,and the influence of different parameters on the vibration characteristics of the pipeline is discussed based on the split-coefficient matrix method.The results exhibit that the different pipe sizes and different flow velocity have important influence on the vibration characteristics of the pipe.Through time-domain and frequency-domain analysis of the water hammer pressure and the axial velocity of the tube wall,the pressure amplitude,the decay rate and the vibration frequency of the pipeline system are discussed to provide some theoretical support for the inhibition and the elimination of vibration damage of the pipe system in the engineering.The experiment is adopted for the modal analysis of the classic reservoir-pipe-valve system,in order to obtain the vibration characteristics of valve-closed water hammer.The vibration amplitude,vibration frequency and natural frequency are discussed by the modal analysis of the pipeline pressure,lateral acceleration and lateral-displacement data.The results indicate that resonance phenomenon occurs when the vibration frequency of the water flow is nearly equal to the natural frequency of the pipe.