Acoustic radiation force on a free elastic sphere in a viscous fluid: Theory and experiments

An expression was derived from the theory for the acoustic radiation force (ARF) acting on a free spherical particle in a viscous fluid subject to an incident plane wave. In deriving this ARF, the viscosity of the fluid, the elasticity of the particle, and the particle's state when suspended freely in the liquid were considered together. Corresponding experiments were designed and conducted. To compare the ARFs measured in experiments with those predicted by theory, a sphere made of polystyrene was taken as the target particle. Based on experimental and theoretical calculations, the effects of the incident sound pressure amplitude, the frequency of the acoustic wave, and fluid viscosity were analyzed. The analysis showed that the ARF increases with increasing pressure amplitude or dynamic viscosity. There is a series of maxima or minima in the ARF that depends on dimensionless frequency kR. Moreover, the theoretical and experimental values are in good agreement. This work provides an advanced ARF theory that is able to predict real-world behavior more accurately.