Acoustic Torques and Forces on Disks

Abstract
The time‐average forces and torques exerted by a plane sound wave upon fixed rigid disks of various shapes are calculated. Results are given for disks bounded by smooth closed convex curves. These results are then specialized to ellipses and circles. Results are also given for infinitely long thin strips. The results are all valid for ka large, where k = 2π/λ, λ being the wavelength and a being a typical dimension of the disk. The oscillatory behavior of the torque as a function of ka and the occurrence of numerous equilibrium positions are interesting consequences of these calculations.