A Wide Bandwidth Study of Ultrasound Velocity and Attenuation in Suspensions: Comparison of Theory with Experimental Measurements

Attenuation and dispersion of antiplane shear waves due to scattering by many two-dimensional cavities

“…Here C is employed instead of n as a measure of the distribution density, following the convention in laboratory experiments. 11,12,[16][17][18][19][20][21][22][23] It may be worth mentioning, however, that the use of C may not be effective if the aspect ratios of scatterers are much deviated from unity. An example is distribution of highly oblate cavities ͑or cracks͒, for which C would remain negligibly small even for considerably large n; there "crack density" nr 3 ͑r is the major axis͒ is conventionally used instead.…”

“…Some researchers measured the amplitude changes and moving speeds of the peaks of transmitting pulses, [22][23][24] whereas others calculated their spectral changes. 12,[17][18][19][20][21] Although the latter method has the advantage of high spectral resolution, the estimates thus obtained could be affected by the incoherent waves included within the pulses. Ensemble averaging of the waveform data was shown to be effective in reducing the incoherent waves as well as noises.…”

“…Ensemble averaging of the waveform data was shown to be effective in reducing the incoherent waves as well as noises. 12,17,19,27 In this article, multiple scattering theories of Foldy,4,5 Waterman and Truell, 7 Lloyd and Berry, 8 and Ye and Ding 13 are compared with numerical-experimentally measured attenuation and phase velocities. To focus on the validity of the theories, numerical experiments are performed as mentioned earlier; antiplane shear wave scattering by 2D circular ͑or parallel cylindrical͒ cavities in elastic media are simulated with high accuracy, closely following Benites et al 24 The attenuation and phase velocities are measured by applying the spectral ratio technique to averaged waveform data, as was successfully done by Suzuki et al 27 Although the model scattering media in the present experiment are rather idealized, it would be a good analog of high-contrast particulate materials and media with small aspect ratio cavities ͑e.g., cracks͒.…”

“…22 On one hand, incorporating such effects appropriately into the theories to bridge this gap is certainly an important task from the practical viewpoint. [18][19][20] On the other hand, using computer simulations of wave scattering free from those effects may be helpful in examining the validity of the theories more directly; though less practical than laboratory ones, numerical experiments could be configured more loyally to the assumptions made in the theories. [24][25][26][27] Another possible reason for the discrepancy among the experimental results may be the variation in the methods to measure the attenuation and phase velocities of coherent waves.…”

Uncertainties in ultrasonic particle sizing in solid-in-liquid suspensions

“…Ultrasonic measurements of attenuation or phase velocity as functions of frequency can be used to estimate Psd. They have the advantage over optical techniques that they can be applied to mixtures that are optically opaque [2]. The technique has been used by, for example, davis [3] to measure mass flow and particle size in coal slurries, Mcclements and Povey [4] to examine aqueous sunflower oil emulsions in the context of the food industry, and Holmes et al [5] to study aqueous suspensions of polystyrene and silica.…”