Web Release Date: November 30,
Influence of Surface-Active Solutes on the Coalescence, Clustering, and Fragmentation of Acoustic Bubbles Confined in a Microspace
and
National Institute of Advanced Industrial Science and Technology (AIST), 2266-98 Shimoshidami, Moriyama-ku, Nagoya 463-8560, Japan, Particulate Fluids Processing Centre, School of Chemistry, University of Melbourne, VIC 3010, Australia, and Particulate Fluids Processing Centre, Department of Chemical and Biomolecular Engineering, University of Melbourne, VIC 3010, Australia
Received: July 11, 2007
In Final Form: October 9, 2007
Abstract:
High-speed imaging was used to capture the effect of surface-active solutes on the behavior of acoustic bubbles, generated in a microspace using low-frequency ultrasound (60 kHz). By confining cavitation within a microspace, the dynamic behavior of bubbles, such as bubble coalescence, clustering, and fragmentation, could be observed directly. It was observed that bubbles coalesced instantly in water; however, in the presence of surface-active solutes (n-propanol and sodium dodecyl sulfate, SDS) the coalescence was hindered. Low-density bubble clusters were observed in the presence of 1 mM SDS and 0.1 M n-propanol. When 0.1 M sodium chloride was added to 1 mM SDS solution, the extent of clustering and the density of the clusters enhanced significantly; a similar observation was made at a higher SDS concentration (10 mM). The importance of these results in understanding multibubble sonoluminescence data published previously has been addressed. The collective oscillation of a bubble cluster consisting of different sized bubbles and images of bubbles emitting a fountain of microbubbles have also been presented.
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