Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/157534

Title

Cavitation microstreaming patterns in single and multiple bubble systems

Author(s)

Tho, Paul;  Manasseh, Richard;  Ooi, Andrew

Abstract

Cavitation microstreaming is a well-known phenomenon; however, few flow visualizations or measurements of the velocity fields have been conducted. In this paper micro-PIV (particle image velocimetry) measurements and streak photography were used to study the flow field around a single and two oscillating bubbles resting on a solid boundary. The mode of oscillation of the bubble was also measured in terms of the variation in the radius of the bubble and the movement of the bubble's centroid so that the streaming flow field could be accurately related to the bubble's oscillatory motion. The mode of oscillation was found to vary primarily with the applied acoustic frequency. Several modes of oscillation were investigated, including translating modes where the bubble's centroid moves along either a single axis, an elliptical orbit or a circular orbit. The flow field resulting from these oscillation modes contains closed streamlines representing vortical regions in the vicinity of the bubble. The translating modes were observed to occur in sequential order with the acoustic excitation frequency, changing from a translation along a single axis, to an elliptical orbit and finally to a circular orbit, or vice versa. Following this sequence, there is a corresponding transformation of the streaming pattern from a symmetrical flow structure containing four vortices to a circular vortex centred on the bubble. Despite some inconsistencies, there is general agreement between these streaming patterns and those found in existing theoretical models. Volume and shape mode oscillations of single bubbles as well as several different cases of multiple bubbles simultaneously oscillating with the same frequency and phase were also investigated and show a rich variety of streaming patterns.

Publication type

Journal article

Source

Journal of Fluid Mechanics, Vol. 576 (Apr 2007), pp. 191-233

Publication year

2007

FOR Code(s)

0102 Applied Mathematics;  0915 Interdisciplinary Engineering

Keyword(s)

Bubbles;  Cavitation microstreaming;  Oscillations

Publisher

Cambridge University Press

ISSN

0022-1120

Publisher URL

http://dx.doi.org/10.1017/S0022112006004393

Copyright

Copyright © 2007 Cambridge University Press.

Peer reviewed