Dual frequency ultrasonic cavitation in various liquids: high-speed imaging and acoustic pressure measurements

Morton, J. A., Khavari, M., Priyadarshi, A., Kaur, A., Grobert, N., Mi, J., Porfyrakis, K., Prentice, P. , Eskin, D. G. and Tzanakis, I. (2023) Dual frequency ultrasonic cavitation in various liquids: high-speed imaging and acoustic pressure measurements. Physics of Fluids, 35(1), 017135. (doi: 10.1063/5.0136469)

Abstract

Ultrasonic cavitation is used in various processes and applications, utilising powerful shock waves and high-speed liquid jets generated by the collapsing bubbles. Typically, a single frequency source is used to produce the desired effects. However, optimisation of the efficiency of ultrasound reactors is necessary to improve cavitation activity in specific applications such as for the exfoliation of two dimensional (2D) materials. This research takes the next step to investigate the effect of a dual frequency transducer system on the bubble dynamics, cavitation zone, pressure fields, acoustic spectra and induced shock waves for four liquids with a range of physical properties. Using ultra-high-speed imaging and synchronised acoustic pressure measurements, the effect of ultrasonic dual frequencies on bubble dynamics was investigated. The addition of a high frequency transducer (1174 kHz) showed that the bubble fragments and satellite bubbles induced from a low frequency transducer (24 kHz) were able to extend their lifecycle, increase spatial distribution, thus, extending the boundaries of the cavitation zone. Furthermore, this combination of ultrasonic frequencies generated higher acoustic pressures (up to 180%) and enhanced the characteristic shock wave peak, indicating more bubble collapses and the generation of additional shock waves. The dual frequency system also enlarged the cavitation cloud size under the sonotrode. These observations specifically delineated the enhancement of cavitation activity using a dual frequency system pivotal for optimisation of existing cavitation-based processing technologies.

• Item Type: Articles
• Additional Information: This work has been funded by the UK Engineering and Physical Sciences Research Council (EPSRC), to the project “Sustainable and industrially scalable ultrasonic liquid phase exfoliation technologies for manufacturing 2D advanced functional materials” (EcoUltra2D), with the grant nos. EP/R031665/1; EP/R031401/1; EP/R031819/1; EP/R031975/1.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Prentice, Dr Paul
• Authors: Morton, J. A., Khavari, M., Priyadarshi, A., Kaur, A., Grobert, N., Mi, J., Porfyrakis, K., Prentice, P., Eskin, D. G., and Tzanakis, I.
• College/School: College of Science and Engineering > School of Engineering > Systems Power and Energy
• Journal Name: Physics of Fluids
• Publisher: American Institute of Physics
• ISSN: 1070-6631
• ISSN (Online): 1089-7666
• Published Online: 08 January 2023
• Copyright Holders: Copyright © 2023 The Authors
• First Published: First published in Physics of Fluids 25(1): 017135
• Publisher Policy: Reproduced under a Creative Commons License