Arbitrary scattering of an acoustical high-order Bessel trigonometric (non-vortex) beam by a compressible soft fluid sphere

The present analysis extends the previous work on the axial acoustic scattering of a high-order Bessel trigonometric beam (HOBTB) from a fluid sphere [F.G. Mitri, J. Appl. Phys. 109 (2011) 014916] to the generalized case of arbitrary scattering from a fluid sphere placed off-axially. The scattered pressure is expressed using a generalized partial-wave series expansion involving the beam-shape coefficients (BSCs), the scattering coefficients of the fluid sphere, and the half-conical angle of the beam. The BSCs are evaluated using the numerical discrete spherical harmonics transform (DSHT). The properties of the off-axial acoustic scattering by a fluid red blood sphere (RBS), chosen as an example to illustrate the analysis, are discussed. 3D numerical computations for the directivity patterns in the near and far-field regions reveal unexplored phenomena that may be useful in applications related to particle entrapment, manipulation or rotation of soft matter using acoustic HOBTBs. Other potential applications may include medical or nondestructive ultrasound imaging with contrast agents, or monitoring of the manufacturing processes of sample soft matter systems with HOBTBs.

► The off-axial acoustic scattering by a fluid red blood sphere is analyzed.
► High-order Bessel trigonometric (non-vortex) beams are considered.
► Emphasis is given to the order of the beam and the amount of the shift.
► The results are important in applications in particle manipulation.