Oscillations of a deformed drop in an acoustic field

Abstract

Because of the importance of acoustic levitation technology and no existing theory of oscillations of deformed drops in acoustic fields, a boundary integral technique, developed by Baker etal. [J. Fluid Med. 123, 477–501 (1982)], has been modified to study oscillations of axisymmetric liquid drops in air. The method consists of determining evolution equations for the position and velocity potential on the surface of the drop. The motion of the surface is determined from the potential by solving an integral equation. The potential is updated every time step by using the Bernoulli equation that depends on gravity, interfacial tension force, and acoustic radiation pressure. The acoustic field is determined for every time step by the Fourier transformation method developed by us. Given initial position and potential along the drop surface, the drop will oscillate around its equilibrium positions where it is statically deformed, which can be computed by introducing numerical damping. Some results on oscillations and frequencies of acoustically deformed drops will be presented. [Work supported by NASA through JPL Contract No. 958722.]