Bjerknes forces between small cavitation bubbles in a strong acoustic field

The mutual interaction between small oscillating cavitation bubbles ${(R}_0<10\mathrm{}\mu \mathrm{m})$ in a strong acoustic field ($P_a>1\mathrm{}\mathrm{bar},$ $f=20\mathrm{}\mathrm{kHz}$) is investigated numerically. We assume spherical symmetry and a coupling of the bubble oscillations. Our results show that the strength and even the directions of the resulting secondary Bjerknes forces differ considerably from predictions of the well-known linear theory. This is of immediate consequence for understanding and modeling structure formation processes in acoustic cavitation and multibubble sonoluminescence.