Acoustic radiation force of a Gaussian beam incident on spherical particles in water.

Based on the finite series method, the Gaussian beam is expanded as spherical functions and the beam coefficient of a Gaussian beam is obtained. A new expression for the acoustic radiation force function, which is the radiation force per unit energy density and unit cross-sectional surface area for a sphere in a Gaussian beam, is presented in this paper. Numerical results for the radiation force function of a Gaussian beam incident upon the spherical particles are presented for rigid spheres, liquid spheres and elastic spheres immersed in water to illustrate the theory. The radiation force function vs. ka curve, ka being the radius times the wavenumber in the surrounding medium, is discussed for different beam widths. The acoustic radiation force function is determined by the parameters of the particles, with liquid spheres having smaller values than those for rigid and elastic spheres. The beam width also affects the acoustic radiation force function. When the radius of the sphere is larger than the beam width, the beam width has greater effects on the radiation force. This analysis helps analyzing and understanding the effects of the acoustic Gaussian beams on spherical objects.