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Abstract
Single clouds of cavitation bubbles, driven by 254kHz focused ultrasound at pressure amplitudes in the range of 0.48-1.22MPa, have been observed via high-speed shadowgraphic imaging at 1×10(6) frames per second. Clouds underwent repetitive growth, oscillation and collapse (GOC) cycles, with shock-waves emitted periodically at the instant of collapse during each cycle. The frequency of cloud collapse, and coincident shock-emission, was primarily dependent on the intensity of the focused ultrasound driving the activity. The lowest peak-to-peak pressure amplitude of 0.48MPa generated shock-waves with an average period of 7.9±0.5µs, corresponding to a frequency of f0/2, half-harmonic to the fundamental driving. Increasing the intensity gave rise to GOC cycles and shock-emission periods of 11.8±0.3, 15.8±0.3, 19.8±0.2µs, at pressure amplitudes of 0.64, 0.92 and 1.22MPa, corresponding to the higher-order subharmonics of f0/3, f0/4 and f0/5, respectively. Parallel passive acoustic detection, filtered for the fundamental driving, revealed features that correlated temporally to the shock-emissions observed via high-speed imaging, p(two-tailed) 200µm diameter, at maximum inflation), that developed under insonations of peak-to-peak pressure amplitudes >1.0MPa, emitted shock-waves with two or more fronts suggesting non-uniform collapse of the cloud. The observations indicate that periodic shock-emissions from acoustically driven cavitation clouds provide a source for the cavitation subharmonic signal, and that shock structure may be used to study intra-cloud dynamics at sub-microsecond timescales.
Original language | English |
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Pages (from-to) | 2151-2158 |
Number of pages | 8 |
Journal | Ultrasonics |
Volume | 54 |
Issue number | 8 |
DOIs | |
Publication status | Published - Dec 2014 |
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Dive into the research topics of 'Periodic shock-emission from acoustically driven cavitation clouds: a source of the subharmonic signal'. Together they form a unique fingerprint.Projects
- 1 Finished
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TheraCav: Harnessing Cavitation for Therapy
Cochran, S. (Investigator), Eisma, R. (Investigator), McGloin, D. (Investigator) & Prentice, P. (Investigator)
COMMISSION OF THE EUROPEAN COMMUNITIES
1/10/13 → 30/09/18
Project: Research
Student theses
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The cavitation subharmonic signal : mechanistic source and optimised detection
Johnston, K. (Author), Prentice, P. (Supervisor), Cochran, S. (Supervisor) & Cuschieri, A. (Supervisor), 2016Student thesis: Doctoral Thesis › Doctor of Philosophy
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