| As the basic component of conveying fluid, pipe is a very common and important engineering structure. Pipe structure has been widely used in aerospace, petrochemical, hydraulic engineering, mechanical engineering and other fields, conveying water, oil, nature gas and so on, which has a broad engineering background. With the improvement of science and technology and the development of modern economy, pipe has been more widely used in production and living and we will encounter more problems, so researches of dynamical properties of pipe structure must be deepened. The analysis of characteristics of wave propagation in the pipe is one of the most important parts in dynamical property analysis, and is extremely meaningful in theory and application.The main contents are as follows:(1) Based on the Flüggle shell theory, using the time-mean Navier-Stokes equations to describe external/internal fluids and static prestress considered as the hydrostatic pressure, vibration equations of a submerged fluid-conveying pipe were obtained; based on the linear potential flow theory, the fluid-structure interaction forces could be expressed as functions of dynamic pressure and viscous shear stresses. Assuming the solutions of the vibration and then substituting them into the vibration equations, we could obtain the nonlinear equation with respect to circular frequency by fluid-structure coupling conditions. Comparing the numerical results of the equation under different conditions, effects of the different modes, hydrostatic pressure and the velocities of the internal and external fluids on the vibration characteristic of the pipe were analyzed.(2) Kelvin-Voigt model, Maxwell model and Standard Linear-solid model were adopted to describe the influence of viscoelastic model, using the time-mean Navier-Stokes equations to describe internal fluid. Wave propagation equations of a fluid-conveying pipe on viscoelastic model were obtained. Assuming the solutions of the wave and then substituting them into the wave propagation equations, we could obtain the nonlinear equation with respect to circular frequency by fluid-structure coupling conditions. Comparing the numerical results of the equation under different conditions, effects of the different radius, wall thickness, velocity of the fluid, damping coefficient and spring stiffness on wave propagation properties in the pipe were discussed. Some useful results were obtained. |
