Acoustic radiation force and torque on a lossless eccentric layered fluid cylinder

Abstract

Exact analytical equations and computations for the longitudinal and transverse acoustic radiation force and axial torque components for a lossless eccentric liquid cylinder submerged in a nonviscous fluid and insonified by plane waves progressive waves (of arbitrary incidence in the polar plane) are established and computed numerically. The modal matching method and the translational addition theorem in cylindrical coordinates are used to derive exact mathematical expressions applicable to any inner and outer cylinder sizes without any approximations, and taking into account the interaction effects between the waves propagating in the layer and those scattered from the cylindrical core. The results show that longitudinal and transverse radiation force components arise, in addition to the emergence of an axial radiation torque component acting on the non-absorptive compound cylinder due to geometrical asymmetry as the eccentricity increases. The computations demonstrate that the axial torque component, which arises due to a geometrical asymmetry, can be positive (causing counter-clockwise rotation in the polar plane), negative (clockwise rotation) or neutral (rotation cancellation) depending on the size parameter of the cylinder and the amount of eccentricity. Furthermore, verification and validation of the results have been accomplished from the standpoint of energy conservation law applied to scattering, and based on the reciprocity theorem.