Bjerknes forces between small cavitation bubbles in a strong acoustic held

The mutual interaction between small oscillating cavitation bubbles (R-0 < 10 mu m) in a strong acoustic field (P-a > 1 bar, f = 20 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 professes in acoustic cavitation and multi-bubble sonoluminescence.