Frequency-dependent acoustic properties of a fluid/porous solid interface

We investigate numerically the frequency dependence of the velocities and damping coefficients of the various surface waves that exist on the interface between a fluid half-space and a half-space of a water-saturated porous Biot medium including viscous attenuation. We find that there is a f1 frequency dependence for pure radiation damping. For a sealed-pore surface configuration, the pseudo-Stoneley wave is radiating at high frequencies, but becomes purely viscosity-damped as frequency decreases. For the open-pore surface configuration, the pseudo-Rayleigh wave remains radiative over the entire frequency domain and is damped by a combination of radiation and viscous fluid–solid interaction. It is also found that the pseudo-Rayleigh wave may even become faster than the bulk shear mode, at low frequencies.