Spiraling bubbles: How acoustic and hydrodynamic forces compete

Experiments to study the effect of acoustic forces on individual bubbles in shear flows have been carried out. In the system that we have used, the co mpetition between acoustic and Fluid dynamical forces results in a spiralin g bubble trajectory. This dynamics is modeled by expressing the balance bet ween Bjerknes and hydrodynamic forces in terms of an ordinary differential equation model, to which a separation of time scales is applied. The succes s of this model shows that the simple force-balance approach is still meani ngful when bubbles are subjected to sound fields.