Translational and radial motions of a bubble in an acoustic standing wave field

Abstract

The dynamic responses of a spherical bubble in an acoustic standing wave field are studied numerically. The equations of motion in the translational and the radial directions are solved simultaneously. It is shown that a bubble which is larger than the resonance size moves to a node of the pressure field and its radial oscillations become small. A sufficiently small bubble is shown to move to an antinode and radially oscillates under the maximum pressure amplitude. It is found using Poincaré maps and power spectra that a bubble which is slightly smaller than the resonance size oscillates chaotically in both the radial and the translational directions. It is demonstrated that the range of the equilibrium bubble size which shows chaotic motions broadens with the pressure amplitude. Finally, the radial responses of the bubble are shown to be dependent not only on the pressure amplitude but also on the drag force in the translational direction.