Acoustic radiation torque of a cylindrical quasi-Gauss beam on a viscoelastic cylindrical shell near an impedance boundary

Abstract

This work presents a comprehensive analytical formalism to calculate the acoustic radiation torque acting on a viscoelastic cylindrical shell near an impedance boundary, which is exerted by a cylindrical quasi-Gauss beam with an arbitrary incident angle propagating in an ideal fluid. An analytical expression in finite series form for the acoustic radiation torque is derived by applying the partial-wave series expansion method, the image theory and the translational addition theorem. Numerical computations for a viscoelastic cylindrical polyethylene shell immersed in water are provided, with particular emphasis on the effects of the reflecting coefficient of the interface, the shell-boundary distance, the position of the shell, the incident angle and the beam waist. Changing the relative thickness and the interior fluid medium are also considered. It is shown that the cylindrical shell can be rotated counter-clockwise or clockwise, depending on the beam frequency, the shell size, the reflecting coefficient and the incident angle. The periodical oscillation of acoustic radiation torque is also observed as the shell moves away from the boundary. The results of this study can improve our understanding of the acoustic radiation torque behaviors for viscoelastic particles near the boundary, which is commonly encountered in biomedical ultrasound and fluid dynamics.