Acoustic microstreaming around an encapsulated particle

Abstract

A theory is suggested to calculate acoustic microstreaming that develops around an encapsulated particle in an ultrasound field. It is assumed that the particle is suspended in an unbounded fluid and can have a gas core or a liquid core. Fluids outside and inside the particle are assumed to be viscous and compressible. No restrictions are imposed on the size of the particle relative to the sound and viscous wavelengths in the outer and inner fluids, and all modes of the particle's motion, including the surface ones, are taken into account. The shell of the particle is assumed to be an elastic viscous compressible medium. Solutions for the sound field within the shell are also valid for any ratio between the particle size and the sound and viscous wavelengths in the shell material. Numerical examples for the cases of an encapsulated gas bubble and an encapsulated particle with a liquid core are presented.