Modelling acoustic cavitation emissions from single to multi-bubble systems

Zhang, Yikai (2026) Modelling acoustic cavitation emissions from single to multi-bubble systems. PhD thesis, University of Glasgow.

Abstract

Acoustic cavitation produces complex emission spectra containing harmonics, subharmonics, and broadband noise. These spectral features are widely used to characterise cavitation activity in applications such as ultrasonic cleaning, sonochemistry, and therapeutic ultrasound. Despite extensive study, the physical mechanisms underlying several characteristic phenomena in cavitation spectra, including broadband noise clearing and hysteresis, remain incompletely understood. This thesis investigates the nonlinear dynamics governing cavitation emissions through a combination of theoretical modelling, numerical simulation, and experimental validation.

A corrected ordinary differential equation formulation of the Kirkwood-Bethe approximation is first derived to model acoustic emissions from oscillating bubbles. The modelling framework is validated using laser-induced cavitation experiments, where bubble radius-time histories obtained from high-speed imaging are reproduced numerically and the emitted pressure field is compared with hydrophone measurements. The results demonstrate good agreement in both bubble dynamics and shockwave emission, establishing confidence in the emission model.

The study then investigates cavitation emissions from interacting bubbles using a fully coupled multi-bubble model informed by experimentally observed bubble distributions. Under a continuously ramped excitation amplitude, both experiments and simulations reproduce the subharmonic route to acoustic chaos and reveal a region of broadband noise clearing. Through spectrogram analysis and stroboscopic mapping of bubble oscillations, this clearing is shown to arise from phase synchronisation of bubble oscillations within the cavitating population.

The analysis is extended to a ramped-then-deramped excitation protocol, where experimental and numerical spectrograms reveal clear asymmetries between ramped and deramped phases at identical excitation amplitudes, demonstrating dynamic hysteresis in cavitation emissions. Using time-history analysis, phase-space trajectories, Poincaré maps, bifurcation diagrams, and basin-of-attraction computations, the hysteresis is shown to originate from the coexistence of multiple attractors in the nonlinear dynamics of interacting bubbles.

Overall, the results establish a physical connection between cavitation emission spectra and the nonlinear dynamics of bubble populations. The findings provide a mechanistic explanation for broadband noise clearing and hysteresis in cavitation emissions and demonstrate the importance of bubble-bubble interactions in determining collective cavitation behaviour.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: T Technology > T Technology (General)
• Colleges/Schools: College of Science and Engineering > School of Engineering
• Supervisor's Name: Prentice, Dr. Paul and Cammarano, Dr. Andrea
• Date of Award: 2026
• Depositing User: Theses Team
• Unique ID: glathesis:2026-86208
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 07 Sep 2026 12:57
• Last Modified: 07 Sep 2026 12:57
• Thesis DOI: 10.5525/gla.thesis.86208
• URI: https://theses.gla.ac.uk/id/eprint/86208

Related URLs

• Article DOI
• Conference proceeding
• Article DOI