Spatio-temporal dynamics of acoustic cavitation bubble clouds

Bubble clouds forming in an extended volume of liquid in acoustic cavitatio n sl-low a slowly varying filamentary structure, whose origin is still not completely understood. Experimental observations are reported that provide some characteristics of the phe nomenon, such as bubble distributions and s ound-field measurements. A discussion of relevant physical interactions in bubbly liquids is comprised of wave dynamics, Bjerknes and drag forces, nuc leation and coalescence. For describing the structure formation process, co ntinuum and particle approaches are employed. In the frame work of the cont inuum model it is shown that homogeneous bubble distributions are unstable, and regions with high bubble concentration emerge in the course of a self- concentration process. In the particle model, all bubbles are treated as in teracting objects that move in the liquid. This approach is complementary t o the continuum model. It allows the inclusion of some particular features, for instance Bjerknes forces based on nonlinear bubble oscillations. Both models are discussed and results are compared with experimentally observed patterns.