Numerical Simulation On FSI Axial Vibration Of Fluid Conveying Viscoelastic Pipes

The fluid conveying pipeline system doesn't only have wide application prospects in industrial productions and people's daily life,but also produces the phenomenon of water hammer because of internal or external factors of pipe.Water hammer has obvious discontinuous wave characteristics in elastic pipeline.Because of viscous and delayed action of viscoelasticity on viscoelastic pipe,discontinuous wave of water hammer will be smooth.But existence of viscoelastic term enhances nonlinear of governing equations under specific boundary conditions.So,we need to look for a numerical method that it can't solve the discontinuous wave problem of water hammer,but also can simply and efficiently solve the viscoelastic problem.This paper applies a newly developed meshless method-finite integration method to simulate response characteristics of axial coupling vibration of elastic and viscoelastic pipes conveying fluid.The research object is reservoir-pipeline-vavle,and the main contents and results are as follows:(1)The four equation model of axial coupling vibration of elastic fluid conveying straight pipe is established by two kind of numerical schemes,whose spatial term is defined by finite integration and time term by the implicit Euler method or numerical inversion of Laplace transform.And that is used to simulate different boundary conditions of simply supported valve and fixed supported valve.Results and comparisons via the results of the proposed numerical schemes in this paper and previous studies verified the superior robustness and stability of finite integration method and greater effects of FSI on the amplitude and phase of axial coupling vibration of fluid conveying straight pipes.Due to numerical inversion of Laplace transform having numerical oscillation by comparison with the results of implicit Euler method,the accuracy and stability of the combination of finite integration method and implicit Euler method is respectively higher and better on water hammer problem.(2)Compared with the results of previous studies,our results verify the superior robustness and stability of finite integration method on the viscoelastic two equations that take into account the steady friction and unsteady friction.By analysing the effects of friction and viscoelasticity in three different conditions that including only considering friction and only considering viscoelasticity and considering their combination,the results indicated that the unsteady friction losses are larger compared with the steady friction on axial vibration of fluid conveying straight pipe,and viscoelastic losses are far greater large than unsteady friction.As the same time,a longer pipe shows a greater loss of friction and a larger viscoelasticity.(3)Based on the viscoelastic two equations of axial vibration,considering the steady friction and unsteady friction affection and applying finite volume method and implicit Euler method to disperse the time terms and the space terms of the government equations and built numerical models,we calculate three numerical models.They are the classical water hammer numerical model of straight water conveying pipes which are considered the friction affection,the numerical model of viscoelastic two equations which are not considered the affection of friction and the numerical model of viscoelastic two equations which are considered the affection of friction respectively.The results are the same as the previous studies.It verifies fim can be used to deal with the affection of tfriction and viscoelasticity precisely and steadily.As the same time,numerical results show friction and viscoelasticity can reduce the axial vibration of pipe and the affection of viscoelasticity is larger than the affection of friction.