Acoustic radiation force and torque on nonspherical scatterers in the Born approximation

Abstract

When the density and bulk modulus of a scatterer are similar to those of the surrounding liquid and the incident sound field is a standing wave, the Born approximation may be used to calculate the acoustic radiation force and torque acting on scatterers of arbitrary shape. The approximation consists of integration over the monopole and dipole contributions to the force acting on each differential volume element within the scatterer. The approach is applied to an axisymmetric scatterer, for which the force and torque may be expressed as an integral along the axis of symmetry. The integral is evaluated analytically for spherical and cylindrical scatterers. The accuracy of the Born approximation is assessed by comparison with the complete solutions for elastic spheres and prolate spheroids based on expansions of the incident and scattered fields in terms of spherical harmonics and spheroidal wave functions, respectively. Results are presented for various particle densities and bulk moduli relative to the surrounding liquid, as well as different shapes, sizes, and orientations of the particle with respect to the standing wave field.When the density and bulk modulus of a scatterer are similar to those of the surrounding liquid and the incident sound field is a standing wave, the Born approximation may be used to calculate the acoustic radiation force and torque acting on scatterers of arbitrary shape. The approximation consists of integration over the monopole and dipole contributions to the force acting on each differential volume element within the scatterer. The approach is applied to an axisymmetric scatterer, for which the force and torque may be expressed as an integral along the axis of symmetry. The integral is evaluated analytically for spherical and cylindrical scatterers. The accuracy of the Born approximation is assessed by comparison with the complete solutions for elastic spheres and prolate spheroids based on expansions of the incident and scattered fields in terms of spherical harmonics and spheroidal wave functions, re...