  A method based on the Rayleigh-Sommerfeld surface integral is provided, which
makes it feasible to rigorously model, evaluate and compute the acoustic
scattering and other mechanical effects of finite-aperture vortex beams such as
the acoustic radiation force and torque on a viscoelastic sphere in various
applications in acoustic tweezers and microfluidics, particle entrapment,
manipulation and rotation. Partial-wave series expansions are derived for the
incident field of acoustic spiraling (vortex) beams, comprising high-order
Bessel and Bessel-Gauss beams.
