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Link between bubble size and subharmonic frequencies of a cavitating ultrasonic horn
The driving mechanism behind ultrasound probes used for mixing and homogenizing is believed to be cavitation. The goal of the project is to study the link between the experimentally observed peaks of acoustic emission from the cavitation and the bubble size as function of excitation amplitude.
Ultrasound probes are widely used for liquid mixing, homogenizing, and even sometimes immersion cleaning purposes. The driving mechanism behind all those phenomena is believed to be cavitation, meaning the periodic formation and collapse of vapor bubbles during the acoustic cycle. The actual cavitation mechanisms contributing to cleaning/mixing are still not well understood, but there is evidence in the literature that the cavitation causes some acoustic emission at fractions of the fundamental forcing frequency. Based on a previous student project, there seems to be a link between the bubble size distribution and those frequencies as function of excitation amplitude.
Ultrasound probes are widely used for liquid mixing, homogenizing, and even sometimes immersion cleaning purposes. The driving mechanism behind all those phenomena is believed to be cavitation, meaning the periodic formation and collapse of vapor bubbles during the acoustic cycle. The actual cavitation mechanisms contributing to cleaning/mixing are still not well understood, but there is evidence in the literature that the cavitation causes some acoustic emission at fractions of the fundamental forcing frequency. Based on a previous student project, there seems to be a link between the bubble size distribution and those frequencies as function of excitation amplitude.
The goal of the project is to confirm (or not) this link experimentally. The bubble size distribution and oscillatory behavior will be determined through high speed imaging. The acoustic emission from the cavitation will be simultaneously measured with a hydrophone and passive cavitation detector. Passive cavitation detectors are special hydrophones designed to have best signal to noise ratio in the low frequency components of periodic shock waves induced by cavitation bubbles and their collapse. The measurements will be performed at different excitation amplitudes of the ultrasound horn. The bubble size distribution and measured acoustic signals will be correlated using the theory of bubble dynamics in an oscillating pressure field.
The goal of the project is to confirm (or not) this link experimentally. The bubble size distribution and oscillatory behavior will be determined through high speed imaging. The acoustic emission from the cavitation will be simultaneously measured with a hydrophone and passive cavitation detector. Passive cavitation detectors are special hydrophones designed to have best signal to noise ratio in the low frequency components of periodic shock waves induced by cavitation bubbles and their collapse. The measurements will be performed at different excitation amplitudes of the ultrasound horn. The bubble size distribution and measured acoustic signals will be correlated using the theory of bubble dynamics in an oscillating pressure field.
For additional information, the candidates can contact Claire Bourquard via email (clairebo at ethz.ch)
For additional information, the candidates can contact Claire Bourquard via email (clairebo at ethz.ch)