Nonlinear dynamics of a solid particle in an acoustically excited viscoelastic fluid. II. Acoustic radiation force

An analytical formula is derived for acoustic radiation force exerted by an axisymmetric acoustic wave on an isotropic solid spherical particle in a compressible viscoelastic fluid. The particle is assumed to undergo pulsation, translation, and shape deformations of all orders. The fluid motion is described by the compressible Oldroyd-B model. No restrictions are imposed on the particle size with respect to the acoustic wavelength and the viscous penetration depth. The obtained analytical formula is used in numerical simulations. The results show that the acoustic radiation force can be increased by more than a factor of 10 due to the viscoelastic nature of the fluid, depending on the parameters. It is also observed that the sign of the force can change so that the force becomes directed to the velocity node instead of the velocity antinode if the driving frequency, the particle size, and the relaxation time of the polymer solution are relatively small.