Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.578927
Title: Cavitation in focused ultrasound
Author: Gerold, Bjoern
Awarding Body: University of Dundee
Current Institution: University of Dundee
Date of Award: 2013
Availability of Full Text:
Access from EThOS:
Access from Institution:
Abstract:
A novel experimental conguration is developed combining a highintensity focused ultrasound source and a pulsed-laser, for the study of cavitation in a eld typical of those used for therapeutic ultrasound. The sonoptic chamber is specically designed to avoid the formation of acoustic standing waves, known to have a critical in uence on cavitation behaviour. A new technique of laser-nucleated acous- tic cavitation is presented, whereby a laser-pulse of energy below the breakdown threshold for the host medium, acts to nucleate acoustic cavitation in a pre-established eld. This facilitates the incorporation of high-speed cameras for interrogation at unprecedented temporal and spatial resolution, combined with acoustic detection directly correlated to the observed cavitation activity. A number of cavitation phenomena are investigated, including bubble-ensemble oscillations at a very early stage of development, in response to the acoustic driving. The frequency of oscillation, which bifurcates with increasing intensity, is also detected in the acoustic emissions. The application of a single-bubble model predicts a source for the acoustic emissions of quiescent radius equivalent to the bubble-ensemble observed, for each intensity investigated. The physical translation of the ensemble, due to the radiation force imposed by the primary eld, is also analysed. For laser-pulses of energy above the breakdown threshold, applying focused ultrasound to the cavity promotes and actuates jet-formation. The characteristics of the so formed jets depend on the intensity and location of the cavity relative to the ultrasound focus.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.578927  DOI: Not available
Share: