Computing the acoustic radiation force exerted on a sphere using the translational addition theorem

Area of Science:

• Acoustics
• Fluid Dynamics
• Wave Scattering

Background:

• Acoustic radiation force is crucial for acoustic manipulation.
• Calculating forces for arbitrary beams and spheres is computationally intensive.
• Existing methods often rely on approximations or numerical integration.

Purpose of the Study:

• To develop a robust analytical method for calculating acoustic radiation force.
• To investigate the trapping capabilities of focused acoustic beams on fluid spheres.
• To compare particle trapping in Rayleigh and Mie scattering regimes.

Main Methods:

• Employing the translational addition theorem for spherical functions.
• Utilizing the partial-wave expansion method with beam-shape coefficients (BSCs) and scattering coefficients.
• Calculating acoustic radiation force for a spherically focused beam on a silicone-oil droplet.

Main Results:

• The translational addition theorem simplifies BSC calculations, avoiding quadrature schemes.
• A paraxial focused beam was shown to exert acoustic radiation force on a fluid sphere.
• Particle trapping was exclusively observed in the Rayleigh scattering regime.

Conclusions:

• The translational addition theorem provides an efficient analytical approach for acoustic radiation force calculations.
• Focused acoustic beams have limitations in trapping particles, particularly in the Mie scattering regime.
• This method advances the understanding of acoustic manipulation and particle trapping.