Analysis Of Fluid-Structure Interaction Effect On Frequency Domain In Delivery Pipeline

Recently, more and more fluid-structure interaction (FSI) problems are put forward in all kinds of engineering field. Vibration and interaction problems of the pipes, as a most representational delivery system, are paid more and more attention.In this thesis, the fundamentals of fluid-structure interaction of pressurized pipe are demonstrated, and the linear differential equations of axial vibration of the delivery pipeline are derived. To get the linear model, the axial and radial vibration were analyzed separately, this assumptions is used in thesis, that fluid-structure interaction works by the contacting effect that is on the border of structure and fluid.Based on the linear differential equations of axial vibration of delivery pipeline and the axial 4-equation model in frequency domain was studied by the Laplace transformation, considering the friction coupling, Poisson coupling and junction coupling between the fluid and the structure.By the description of system vibration in time domain, the system vibration in frequency domain was obtained, and the basic equation and conditions are confirmed.The axial 4-equation model in frequency domain was resolved separately by the method of characteristics and the method of transfer matrix. The corresponding computer code was developed on the platform of FORTRAN90, the results from calculation was compared with that from classic model, in considering of the corresponding effect of fluid-structure interaction.Based on above means, the vibration of system in frequency domain has been analyzed. The frequency and modes of the vibration were confirmed by the boundary conditions. From the example of resolving the frequency of the vibration of a simple RPV system, 1-7 modes are determined. The characteristic of dispersion, dissipation of system and the effect to system of damping ratio in the case of sudden valve-closure are concluded, the curve of dynamic characteristic describing the effect of different damping ratio to the system was drawn and the impact of pipe characteristic on interaction has been discussed. It has been conducted that different material and pipe size play the important roles on the pipe vibration with fluid-structure interaction. The water-hammer pressure can be reduced effectively by optimizing the parameters, through which transport pipe system works more safely.