Numerical Modeling And Analysis On Two-phase Flow And Fluid-induced Vibration Of Elastic Pipes

The problems of the gas-liquid two-phase flow in pipelines and its fluid-induced vibration(FIV)are widely encountered in nuclear power industry,chemical industry and other fields.When strong fluid induced vibration occurs in pipelines,pipes and their support structures will be damaged with fatigue failure,which leads to accidents.The unsteadiness of two-phase flow and pressure pulsation are the main sources of the fluidinduced vibrations of elastic pipes.The fluid parameters of two-phase flow vary with time and the interface of the two-phase is complex.Furthermore,complicated fluid-structure interaction problems correlate to the FIV phenomenon.This thesis aims to establish numerical methods for analyzing two-phase flow and fluid-induced vibration and provides physical insights into the relationship among the flow pattern,fluid pressure and the vibration of pipes.The fluid-structure interaction of pipelines with large aspect ratio is considered.A partitioned numerical method is established to analyze the FIV features of the pipes.A one-dimensional numerical model for two-phase flow is developed based on the finite volume scheme,in which the numerical flux between adjacent finite control volumes is calculated by the HLLC scheme.The one-dimensional method for single phase flow can be applied to two-phase flow by using homogeneous equilibrium model of two-phase flow.A semi-analytical numerical model for vibration analysis of cylindrical shells is constructed on the basis of the finite element method.The fluidinduced vibration of pipes is analyzed with a loosely coupled method.The above research provides an efficient calculation method with the analysis of the FIV of pipelines with large aspect ratio.A strongly coupled fluid-structure interaction numerical model is used for vibration analysis of elastic pipes containing gas-liquid two-phase flow.The volume of fluid(VOF)model is adopted to capture the interface of the gas and liquid phase.The vibration responses of pipelines subject to twophase flow is analyzed.The relationship among the fluid pressure spectrum,the natural frequency of pipes and their vibration response is discussed.Experiments on the free vibrations and FIV of elastic pipes conveying single-phase and two-phase flow are carried out.The numerical methods of fluid-induced vibration of elastic pipes and the physical insights into the relationship between fluid pressure and FIV responses of pipes provide technical support for the design of the pipelines in nuclear industry,chemical industry and other fields.