ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

4pPA4. Nonlinear bubble oscillations and Bjerknes forces.

Sean M. Cordry

Dept. of Phys., Univ. of Mississippi, University, MS 38677

Lawrence A. Crum

Ronald A. Roy

Appl. Phys. Lab., Seattle, WA 98105

The acoustic levitation of bubbles in standing waves has been considered by many authors. Calculations of the equilibrium levitation position have followed the example of Eller [A. Eller, 170--171 (1968)] by considering linear radial pulsations whose amplitude is given by a linearized Rayleigh--Plesset equation. This procedure begins to fail as the bubble starts behaving in a nonlinear fashion. For bubbles experiencing nonlinear behavior, the radiation pressure (primary Bjerknes force) must be numerically calculated from the product of the instantaneous bubble volume and the pressure gradient of the sound field. Bubbles smaller than resonance size are normally attracted to the pressure antinode, but when nonlinear effects are considered, the bubbles can be repulsed by the pressure antinode for driving pressures above a certain threshold amplitude. Results of our calculations will be presented along with the implications for single bubble sonoluminescence. [Work supported by the office of Naval Research.]