Propagation characteristics of guided waves in a liquid filled pipe embedded in a porous medium

A model of a liquid-filled pipe embedded in a porous medium is built to research its wave propagation characteristics,and to analyze the effect of the parameters of porous media on the dispersion.The dispersion equations are established on the basis of the elastic-dynamic theory of the liquid-saturated porous solid.The characteristic of dispersion and the time domain waveform in pipes of different thicknesses and with different porous-medium parameters are discussed theoretically and numerically.Results reveal that the porosity has little impact on dispersion,and the attenuation of guided wave increases with porosity,whilst the porosity influences the displacement amplitude of the time domain waveform.It is hard to detect the permeability variation of the media by the dispersion.The drawn conclusion can provide some theoretical instruction and guidance for the nondestructive testing of buried pipe.

Propagation characteristics of low-frequency axisymmetric waves in fluid-filled pipes embedded in the viscoelastic medium

The propagation characteristics of the low-frequency axisymmetric waves in buried fluid-filled pipes are investigated theoretically,based on the Kennard thin-walled shell equations,the Helmholtz equation,and the Kelvin-Voigt linear viscoelastic model.Analytic expressions of the phase velocity are derived for both the fluid-dominated wave and the shell-compressed wave under lubricated contact,via considering the surrounding soil as a viscoelastic medium.The dispersion and attenuation curves of the two wave types are obtained and verified numerically.The ratio of the radial pipe wall displacements is analyzed,with particular emphasis on the effects of the thickness-to-radius ratio and the quality factor on the dispersion and attenuation characteristics of the fluid-dominated wave.The results show that the viscoelastic property has slight effects on the phase velocities of the two wave types,but it influences the attenuation severely.The fluid-dominated wave influences the radial pipe wall displacement significantly and is the primary carrier of leakage noise energy;its phase velocity increases as a function of the thickness-to-radius ratio while the attenuation decreases.It also shows that the dispersion and attenuation of the fluid-dominated wave decrease as a function of the quality factor.The work will provide insights and guidance for the leakage detection of buried fluid-filled pipes.

Interface wave propagation characteristics of liquid-immersed porous cylinder

This paper devotes to investigate the propagation characteristics of the interface wave on the liquid-immersed porous cylinder, and special emphasis is paid on the dependence of the dispersion relation on the porous media parameters. A model of liquid-immersed porous cylinder is established theoretically. Based on the elastic-dynamic theory of liquid-saturated porous solid and wave theory, the dispersion curves and transient response of open-pores and sealed-pores are simulated numerically, and their dependence on the cylinder radius and porous medium parameters are analyzed. The results show that the Stoneley-Scholte wave can be clearly distinguished with other waves in the time domain, and the Stoneley-Scholte wave dispersion relates intimately with the porosity of the porous medium and cylinder radius, whilst the permeability of the media has little effect on the dispersion property.