Iterative modelling of sound field and bubble distribution in acoustic cavitation
* Presenting author
Abstract:
Acoustic cavitation is the nucleation and dynamics of bubbles in strong sound fields in liquids. When bubbles occur, they are driven by acoustic (Bjerknes) forces to move in space, arrange in structures, and potentially merge. On the other hand, the presence of gaseous voids can have significant influence on the sound propagation in the liquid, and thus can alter the acoustic field. Since the bubble motion and distribution depends on the field properties, the mutual interaction of bubbles and field might result in a complicated evolution. Here we present a numerical model to capture essentials of this coupling. An iterative scheme alternately determines for a time step the bubble motion on basis of discrete particles, and adapts the continuous pressure field via solving a modified Helmholtz equation. The field equation is based on the model by Louisnard which takes into account nonlinear oscillations and damping of the bubbles. The discrete bubble population is included as a smeared-out bubble density. The numerical method is applied to the temporal evolution of an ensemble of bubbles seeded by a laser pulse in concentrated phosphoric acid driven by an ultrasonic standing wave field.