The acoustic radiation force on a spherical thermoviscous particle in a thermoviscous fluid including scattering and microstreaming

TL;DR

This paper develops comprehensive analytical formulas for the acoustic radiation force on small spherical particles in fluids, accounting for complex effects like scattering, microstreaming, and heat conduction, applicable to various particle and fluid types.

Contribution

It introduces a unified analytical framework that includes effects often neglected, such as heat conduction and temperature-dependent viscosity, without restrictions on boundary layer widths.

Findings

The formulas agree with previous theories in certain limits.

Significant deviations occur for specific particle and fluid combinations.

The theory encompasses both elastic solid and fluid particles.

Abstract

We derive general analytical expressions for the time-averaged acoustic radiation force on a small spherical particle suspended in a fluid and located in an axisymmetric incident acoustic wave. We treat the cases of the particle being either an elastic solid or a fluid particle. The effects of particle vibrations, acoustic scattering, acoustic microstreaming, heat conduction, and temperature-dependent fluid viscosity are all included in the theory. Acoustic streaming inside the particle is also taken into account for the case of a fluid particle. No restrictions are placed on the widths of the viscous and thermal boundary layers relative to the particle radius. We compare the resulting acoustic radiation force with that obtained from previous theories in the literature, and we identify limits, where the theories agree, and specific cases of particle and fluid materials, where qualitative or significant quantitative deviations between the theories arise.