Oscillations, Waves, and Interactions - GWDG

Oscillations, Waves and Interactions, pp. 171–198
edited by T. Kurz, U. Parlitz, and U. Kaatze
Universitätsverlag Göttingen (2007) ISBN 978–3–938616–96–3
urn:nbn:de:gbv:7-verlag-1-07-3
From a single bubble to bubble structures
in acoustic cavitation
Robert Mettin
Drittes Physikalisches Institut, Georg-August-Universität Göttingen
Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
Abstract. The article reviews main ingredients for a bottom-up approach to understand
and model acoustic cavitation structures. Based upon the dynamics of a single, spherical
bubble in a sound field, the fate of a bubble in a given acoustic set-up and collective
behaviour in multibubble systems are derived. The discussion includes nucleation and oscillation
of bubbles, their shape stability, and rectified gas diffusion. Furthermore, acoustic
forces on pulsating bubbles and bubble translation are addressed. The different aspects are
combined in bubble life cycle diagrams, and a particle model for the description of many
interacting bubbles is proposed. The application of this method for numerical simulation of
experimentally observed acoustic cavitation structures is demonstrated by examples.
1 Introduction
The expression acoustic cavitation describes the physical phenomenon of rupture of
a liquid under tension caused by a sound wave [1–6]. Apart from the creation of
voids in the liquid itself, which is termed inception, acoustic cavitation comprises as
well the further destiny of the voids. This leads directly to the main subjects bubble
dynamics, bubble collapse, and bubble structure formation. An important issue is
also the transformation of the non-cavitating liquid into a two-phase fluid of gas and
liquid after cavitation inception. Among other effects, this can cause a retroaction of
cavitation on the generating sound field.
All the above items, taken alone, are already challenging research topics and not
understood in every detail yet. Taken all together, we can rightly characterize acoustically
cavitating liquids as complex systems. Complicating aspects for a general
theoretical treatment of acoustic cavitation and the accompanying phenomena are
especially nonlinearity, time and space scales that span many orders of magnitude,
and granularity (i. e., properties somehow intermediate between continuous and discrete).
Accordingly, investigations in this area often attack partial problems and
idealized cases to reach a better and better understanding and description of the
observations, though still being far from a general and complete picture.
In recent time, the demand for an improved knowledge of acoustic cavitation has
grown constantly, because the field of applications is permanently extending. Be-