Finite static deformation and translational motion of an acoustically levitated liquid drop in air.

Abstract

Acoustical levitation has been applied in studies of droplet dynamics and interfacial properties. On the ground, when the density difference between droplet and host medium is large, the intensity of the levitation sound field must be strong enough to overcome gravity. As a result, the droplet may significantly deviate from spherical shape. A numerical method to determine the finite deformation and location of an acoustically levitated liquidated liquid drop in air has been developed. Compared with the previous studies [P. L. Marston, J. Acoust. Soc. Am. 67, 15–26 (1980) and H. W. Jackson etal., J. Acoust. Soc. Am. 84, 1845–1862 (1988)], the interactions between droplet and sound field and the nonspherical acoustical scattering are included in our analysis, making the present method valid for droplets with aspect ratio as large as 2. With this method, the droplet shapes and locations as functions of sound pressure, surface tension, and droplet volume in both gravity and nongravity environments have been systematically calculated. The numerical results agree well with these experimental measurements and those of Trinh and Hsu [J. Acoust. Soc. Am. 79, 1335–1338 (1986)]. [Work supported by NASA through JPL, Contract No. 958722.]