Abstract (Invited)

A Three-Dimensional View on Bubbles

W.Lauterborn, R.Mettin, D.Krefting, J.Appel (Drittes Physikalisches Institut, Universitaet Goettingen, Goettingen, Germany)

e-mail: W.Lauterborn@dpi.physik.uni-goettingen.de

Acoustic cavitation bubbles in ultrasonic standing wave fields tend to organize themselves in dynamic structures resembling dendritic filaments. They follow nonlinear acoustic forces induced by the acoustic field and by the interaction between the oscillating bubbles (the Bjerknes forces). To gain information about the motion of bubbles in an acoustically cavitating liquid a stereoscopic high speed cinematographic arrangement with two synchronized CCD-cameras is employed. Maximum framing rate is 2250 frames per second and the maximum observation time is 7.28 seconds at this speed. Via digital picture processing from the two picture streams the three-dimensional position of the bubbles can be determined and by particle tracking from frame to frame their motion giving the complete space - time dynamics of bubble clouds. Examples of bubble tracks in cavitation bubble fields at sound field frequencies around 20 kHz and of velocity distributions are given and compared with theoretical models of oscillating and interacting bubbles.

Section : 4