Effect of local fluid flow on the propagation of plane waves at an interface of water/double-porosity solid with underlying uniform elastic solid

This study deliberates the propagation of acoustic wave at water/double-porosity sediment interface with an underlying uniform elastic solid substrate. A mathematical model is constituted through three layers with distinct elastic properties. This layered structure contains an isotropic double-porosity solid sandwiched between an overlying water and underlying uniform elastic solid. The sandwiched layer is of finite thickness. Two types of boundary conditions (impermeable and permeable) at the interface of double-porosity solid and elastic solid substrate are considered. The closed form analytical expressions for reflection and transmission coefficients are derived theoretically for appropriate boundary conditions. These expressions are calculated as a non-singular system of linear algebraic equations. This non-singular system depends on various material parameters. Therefore, a numerical example is used to determine the effects of various properties of sandwiched layer on reflection and transmission coefficients. Essences of wave frequency, incident direction, layer thickness, pore fluid viscosity, wave-induced fluid flow and sealing of boundary pores on reflection and transmission coefficients are depicted graphically and discussed elaborately. It is revealed that the presence of double-porosity layer has a significant effect on reflection and transmission coefficients.