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

## 4pPA4. Nonlinear bubble oscillations and Bjerknes forces.

**Sean M. Cordry
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*Dept. of Phys., Univ. of Mississippi, University, MS 38677
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**Lawrence A. Crum
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Ronald A. Roy
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*Appl. Phys. Lab., Seattle, WA 98105
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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.]