Cavitation events create extreme conditions in a localized ‘bubble collapse’ region, leading to the formation of hydroxyl radicals, shockwaves and microscopic high-speed jets, which are useful for many chemical and physical transformation processes. Single bubble dynamics equations have been used previously to investigate the chemical and physical effects of cavitation. In the present study, the state of the art of the single bubble dynamics equations was reviewed and certain noteworthy modifications were implemented. Simulations reaffirmed previously reported collapse temperatures of the order ~5,000 K and collapse pressures well over ~1,000 bar under varying operating conditions. The chemical effects were assessed in terms of the hydroxyl radical generation rate (OHG), calculated by applying the minimization of the Gibb's Free Energy method using simulated collapse conditions. OHG values as high as 1x1012 [rad]OH molecules per collapse event were found under certain operating conditions. A new equation was proposed to assess the physical effects, in terms of the impact pressure of the water jet - termed as the jet hammer pressure (JHP), formed due to the asymmetrical collapse of a bubble near a wall. The predicted JHP were found to be within a range of ~100 to 1000 bar under varying operating conditions. Important issues such as the onset of cavitation and chaotic solutions, for a cavitating single bubble dynamics were discussed. The Blake threshold pressure was found to be a sufficient criterion to capture the onset of cavitation. The impact of key operating parameters on the chemical and physical effects of cavitation were investigated exhaustively through simulations, over the parameter ranges relevant to acoustic and hydrodynamic cavitation processes. Presented methodology and results will be useful for optimisation and further investigations of a broad range of acoustic and hydrodynamic cavitation-based applications.
Bibliographical noteFunding Information:
The authors would like to thank Prof. A. B. Pandit and his research group for their help for developing the simulation code. The authors would also like to thank the Leverhulme project (RPG-2019-127) for providing the funding to enable this research.
© 2021 The Author(s)
Copyright 2021 Elsevier B.V., All rights reserved.
- Cavitation jets
- Hydrodynamic - acoustic cavitation
- Hydroxyl radicals
- Localised energy dissipation
ASJC Scopus subject areas
- Chemical Engineering (miscellaneous)
- Environmental Chemistry
- Radiology Nuclear Medicine and imaging
- Acoustics and Ultrasonics
- Organic Chemistry
- Inorganic Chemistry