Abstract
Upon application of ultrasonic waves to a suspension of solid particles in liquid, multiple scattering occurs at the particle/liquid interfaces leading to attenuation. It was recently shown through experimental verification that multiple scattering theory must include shear wave influences at the boundary between the liquid and solid particles in a nanofluid when the concentration of the scatterers is even as low as a few percent by volume. Herein, we consider silica spheres of 50–450 nm diameter in the long-wavelength regime to elucidate the form of the shear decay fields at the liquid/solid interface for individual particles. This is important because the overlap of these fields ultimately leads to the conversion of a compressional wave to shear waves and back into the compressional wave, the effect originating due to the density contrast between the particle and the liquid. Therefore, we examine in detail the velocity, vorticity and viscous dissipation in the shear wave field and around the silica spheres using finite element modelling, giving clarity to the viscous boundary effects. We also compare the numerical modelling to semi-analytical results.
Highlights
In the analysis of solid particles in liquids, the size, density, etc. of the scatterer is perhaps best evaluated through ultrasonic spectroscopy when the concentration is high enough to make the sample impenetrable by light[1,2,3]
Our ultimate aim is to investigate particle interactions through the shear field, here we present the results of the simulations for a single particle and show www.nature.com/scientificreports the effect of particle size and frequency on shear wave field effects to establish the single particle effects before studying particle interactions
We have demonstrated the finite element analysis of a series of single solid particles of differing sizes in water as they interact with an ultrasonic plane wave
Summary
In the analysis of solid particles in liquids, the size, density, etc. of the scatterer is perhaps best evaluated through ultrasonic spectroscopy when the concentration is high enough to make the sample impenetrable by light[1,2,3]. Fields around a single (solid) silica particle with diameter 50 nm to 450 nm in water, and the influence of particle size and frequency on the wave amplitude, wavelength, and viscous dissipation in the region of the particle. These simulations act as a building block for the investigation of the interactions between particles mediated by the shear fields in concentrated or aggregated particle systems.
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