Incoherent Waves in Fluid-Saturated Sintered Granular Systems: Scattering Phenomena

Abstract

The incoherent transport of ultrasound waves in water-saturated sintered glass bead packings is experimentally investigated. The spectral energy density of scattered high-frequency waves is explained by a diffusion wave equation. Immersion broadband transducers with central frequencies of 1 MHz are positioned at a distance of 73 mm to the porous sample. The diffusion coefficient and quality factor are predicted from a diffusion approximation of the time-dependent intensity curve to the ensemble-averaged measurement data. From the diffusion coefficient, we deduce a mean-free path for scattering events at l*=0.87±0.03 mm close to the range of particle diameters of the samples (1.0<dp<1.2 mm). Results are in good agreement with observations from Jia (2004, “Codalike Multiple Scattering of Elastic Waves in Dense Granular Media,” Phys. Rev. Lett., 93(15), p. 154303) observed for nonsintered and consolidated bead packings (0.6<dp<0.8 mm). The low-quality factor Q=190±10 indicates a high amount of intrinsic damping of the scattered waves although water was used as saturating and coupling fluid.