Research On Fluid-Structure Interaction Calculation Of Conveying Fluid Pipes

The Fluid-Structure Interaction(FSI)is an inevitably phenomenon which happens when the pipe conveying fluid are used.Considering the FSI is very important when we are working on the vibration characteristics of pipeline system.It can be said that the studying of the FSI calculation of pipeline is an important link in the design and optimization of piping systems.It is also a hot topic in the fields of naval architecture and ocean engineering,water resources and hydropower engineering,petrochemical and energy engineering,and other related engineering fields.Firstly,in this paper two different FSI models are established for different pipeline systems--14 equations based on beam model and 8 equations based on thin-shell model.For the beam model,the mathematical model is established using Timoshenko beam theory.The field transfer matrix is obtained by the Laplace transformation.Then the field transfer matrix of axially symmetric variable cross-section pipeline element can be obtained by Magnus series method.For the thin-shell model,the Goldenveizer-Novozhilov thin-shell theory is used to establish the mathematical model.The field transfer matrix in circumferential direction is obtained by analyzing the axial direction through the separating variable method and the wave decomposition method which are combined with the boundary conditions.We will introduce the precise integration method(PIM)and explain the self-adaptability of the two parameters in detail,then use the two methods to solve the field transfer matrix.In the end,we will prove the model and the algorithm are accurate and efficient by two examples.Secondly,based on the theoretical model,the dimensionless method is used to study the influences of several dimensionless parameters on the stability,low-order inherent characteristics and response characteristics of piping system,and get some basic laws of pipeline vibration.These will provide some valuable references for further study of vibration and engineering practice of pipeline structures.When the ratio of thickness to length(_RL)and the ratio of thickness to inner radius(_Re)are kept constant,the natural frequency of the system is independent of the pipeline structure parameter,but the dimensionless amplitude decreases with the increase of the structural parameters.Whene_Rremains constant,the natural frequency of the system increases with the increase ofL_R,while the dimensionless amplitude increases with the increase ofe_Rand then remains unchanged.And the influence ofL_Ron the vibration characteristics of the piping system is greater thane_R.The natural frequency of the piping system decreases as the fluid dimensionless parameter increases,and the amplitude does not change.In addition,there is no relationship between the dimensionless vibration characteristics of the piping system and the structural fluid parameter ratio.Finally,Combined with the actual pipeline system,the feasibility of this model and the algorithm in the calculation of complex piping system is verified by simulation and experiment.