Tonry, C.E.H. ORCID: 0000-0002-8214-0845 , Djambazov, G. ORCID: 0000-0001-8812-1269 , Dybalska, A., Griffiths, W.D., Beckwith, C., Bojarevics, V. ORCID: 0000-0002-7326-7748 and Pericleous, K.A. ORCID: 0000-0002-7426-9999 (2020) Acoustic resonance for contactless ultrasonic cavitation in alloy melts. Ultrasonics Sonochemistry, 63:104959. ISSN 1350-4177 (doi:https://doi.org/10.1016/j.ultsonch.2020.104959)

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Abstract

Contactless ultrasound is a novel, easily implemented, technique for the Ultrasonic Treatment (UST) of liquid metals. Instead of using a vibrating sonotrode probe inside the melt, which leads to contamination, we consider a high AC frequency electromagnetic coil placed close to the metal free surface. The coil induces a rapidly changing Lorentz force, which in turn excites sound waves. To reach the necessary pressure amplitude for cavitation with the minimum electrical energy use, it was found necessary to achieve acoustic resonance in the liquid volume, by finely tuning the coil AC supply frequency. The appearance of cavitation was then detected experimentally with an externally placed ultrasonic microphone and confirmed by the reduction in grain size of the solidified metal. To predict the appearance of various resonant modes numerically, the exact dimensions of the melt volume, the holding crucible, surrounding structures and their sound properties are required. As cavitation progresses the speed of sound in the melt changes, which in practice means resonance becomes intermittent. Given the complexity of the situation, two competing numerical models are used to compute the soundfield. A high order time-domain method focusing on a particular forcing frequency and a Helmholtz frequency domain method scanning the full frequency range of the power supply. A good agreement is achieved between the two methods and experiments which means the optimal setup for the process can be predicted with some accuracy.

Item Type:	Article
Additional Information:	© 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/).
Uncontrolled Keywords:	ultrasonic processing, acoustic cavitation, computational acoustics, metals processing
Subjects:	Q Science > QA Mathematics Q Science > QA Mathematics > QA75 Electronic computers. Computer science
Faculty / School / Research Centre / Research Group:	Faculty of Engineering & Science > Centre for Numerical Modelling & Process Analysis (CNMPA) Faculty of Engineering & Science > Centre for Numerical Modelling & Process Analysis (CNMPA) > Computational Science & Engineering Group (CSEG) Faculty of Engineering & Science > School of Computing & Mathematical Sciences (CMS) Faculty of Engineering & Science
Last Modified:	04 Mar 2022 13:06
URI:	http://gala.gre.ac.uk/id/eprint/26514

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