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dc.contributor.authorJohnston, Keitheng
dc.contributor.authorTapia-Siles, Ceciliaeng
dc.contributor.authorGerold, Bjoerneng
dc.contributor.authorPostema, Michieleng
dc.contributor.authorCochran, Sandyeng
dc.contributor.authorCuschieri, Alfredeng
dc.contributor.authorPrentice, Pauleng
dc.date.accessioned2015-03-25T12:52:40Z
dc.date.available2015-03-25T12:52:40Z
dc.date.issued2014-12eng
dc.identifier.issn0041-624Xen_US
dc.identifier.urihttps://hdl.handle.net/1956/9645
dc.description.abstractSingle clouds of cavitation bubbles, driven by 254 kHz focused ultrasound at pressure amplitudes in the range of 0.48–1.22 MPa, have been observed via high-speed shadowgraphic imaging at 1 × 10⁶ 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 0.48 MPa generated shock-waves with an average period of 7.9 ± 0.5 μs, 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 ± 0.2 μs, at pressure amplitudes of 0.64, 0.92 and 1.22 MPa, 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) < 0.01 (r = 0.996, taken over all data). Subtracting the isolated acoustic shock profiles from the raw signal collected from the detector, demonstrated the removal of subharmonic spectral peaks, in the frequency domain. The larger cavitation clouds (>200 μm diameter, at maximum inflation), that developed under insonations of peak-to-peak pressure amplitudes >1.0 MPa, 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.en_US
dc.language.isoengeng
dc.publisherElsevieren_US
dc.rightsAttribution-NonCommercial-NoDerivs CC BY-NC-NDeng
dc.rights.urihttp://creativecommons.org/licenses/by-nc-nd/3.0/eng
dc.subjectAcoustic cavitationeng
dc.subjectSubharmoniceng
dc.subjectCloud dynamicseng
dc.subjectCollapseeng
dc.subjectShock-waveeng
dc.titlePeriodic shock-emission from acoustically driven cavitation clouds: a source of the subharmonic signalen_US
dc.typePeer reviewed
dc.typeJournal article
dc.date.updated2015-03-04T07:57:47Zen_US
dc.description.versionpublishedVersionen_US
dc.rights.holderCopyright 2014 The Authorsen_US
dc.identifier.doihttps://doi.org/10.1016/j.ultras.2014.06.011
dc.identifier.cristin1141240
dc.source.journalUltrasonics
dc.source.4054
dc.source.148
dc.source.pagenumber2151-2158
dc.subject.nsiVDP::Mathematics and natural scienses: 400::Physics: 430::Electromagnetism, acoustics, optics: 434en_US
dc.subject.nsiVDP::Matematikk og naturvitenskap: 400::Fysikk: 430::Elektromagnetisme, akustikk, optikk: 434nob


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