Equivalence between angular spectrum-based and multipole expansion-based formulas of the acoustic radiation force and torque.

ABSTRACT

Two main methods have been proposed to derive the acoustical radiation force and torque applied by an arbitrary acoustic field on a particle The first one relies on the plane wave angular spectrum decomposition of the incident field (see Sapozhnikov and Bailey [J. Acoust. Soc. Am. 133, 661-676 (2013)] for the force and Gong and Baudoin [J. Acoust. Soc. Am. 148, 3131-3140 (2020)] for the torque), while the second one relies on the decomposition of the incident field into a sum of spherical waves, the so-called multipole expansion (see Silva [J. Acoust. Soc. Am. 130, 3541-3544 (2011)] and Baresch, Thomas, and Marchiano [J. Acoust. Soc. Am. 133, 25-36 (2013)] for the force, and Silva, Lobo, and Mitri [Europhys. Lett. 97, 54003 (2012)] and Gong, Marston, and Li [Phys. Rev. Appl. 11, 064022 (2019)] for the torque). In this paper, we formally establish the equivalence between the expressions obtained with these two methods for both the force and torque.