Comparison of frequency domain and time domain methods for the numerical simulation of contactless ultrasonic cavitation
The use of a top-mounted electromagnetic induction coil has been demonstrated as a contactless alternative to traditional ultrasonic treatment (UST) techniques that use an immersed mechanical sonotrode for the treatment of metals in the liquid state. This method offers similar benefits to existing U...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Elsevier
2022-09-01
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| Series: | Ultrasonics Sonochemistry |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S1350417722002346 |
| _version_ | 1798031798738878464 |
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| author | Christopher Beckwith Georgi Djambazov Koulis Pericleous Catherine Tonry |
| author_facet | Christopher Beckwith Georgi Djambazov Koulis Pericleous Catherine Tonry |
| author_sort | Christopher Beckwith |
| collection | DOAJ |
| description | The use of a top-mounted electromagnetic induction coil has been demonstrated as a contactless alternative to traditional ultrasonic treatment (UST) techniques that use an immersed mechanical sonotrode for the treatment of metals in the liquid state. This method offers similar benefits to existing UST approaches, including degassing, grain refinement, and dispersion of nanoparticles, while also preventing contact contamination due to erosion of the sonotrode. Contactless treatment potentially extends UST to high temperature or reactive melts. Generally, the method relies on acoustic resonance to reach pressure levels suitable for inertial cavitation and as a result the active cavitation volume tends to lie deep in the melt rather than in the small volume surrounding the immersed sonotrode probe. Consequently, (i) with suitable tuning of the coil supply frequency for resonance, the treatment volume can be made arbitrarily large, (ii) the problem of shielding and pressure wave attenuation suffered by the immersed sonotrode is avoided. However, relying on acoustic resonance presents problems: (i) the emergence of bubbles alters the speed of sound, resonance is momentarily lost, and cavitation becomes intermittent, (ii) as sound waves travel through and reflect on all the materials surrounding the melt, the sound characteristics of the crucible and supporting structures need to be carefully considered. The physics of cavitation coupled with this intermittent behaviour poses a challenge to sonotrode modelling orthodoxy, a problem we are trying to address in this publication. Two alternative approaches will be discussed, one of which is in the time domain and one in the frequency domain, which couple the solution of a bubble dynamics solver with that of an acoustics solver, to give an accurate prediction of the acoustic pressure generated by the induction coil. The time domain solver uses a novel algorithm to improve simulation time, by detecting an imminent bubble collapse and prescribing its subsequent behaviour, rather than directly solving a region that would normally require extremely small time steps. This way, it is shown to predict intermittent cavitation. The frequency domain solver for the first time couples the nonlinear Helmholtz model used for studying cavitation, with a background source term for the contribution of Lorentz forces. It predicts comparable RMS pressures to the time domain solver, but not the intermittent behaviour due to the underlying harmonic assumption. As further validation, the frequency domain method is also used to compare the generated acoustic pressure with that of traditional UST using a mechanical sonotrode. |
| first_indexed | 2024-04-11T20:02:17Z |
| format | Article |
| id | doaj.art-3e6163806cc34ac1814fcdc0b85910d6 |
| institution | Directory Open Access Journal |
| issn | 1350-4177 |
| language | English |
| last_indexed | 2024-04-11T20:02:17Z |
| publishDate | 2022-09-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Ultrasonics Sonochemistry |
| spelling | doaj.art-3e6163806cc34ac1814fcdc0b85910d62022-12-22T04:05:31ZengElsevierUltrasonics Sonochemistry1350-41772022-09-0189106138Comparison of frequency domain and time domain methods for the numerical simulation of contactless ultrasonic cavitationChristopher Beckwith0Georgi Djambazov1Koulis Pericleous2Catherine Tonry3Corresponding author.; Computational Science and Engineering Group, University of Greenwich, 30 Park Row, London SE10 9LS, UKComputational Science and Engineering Group, University of Greenwich, 30 Park Row, London SE10 9LS, UKComputational Science and Engineering Group, University of Greenwich, 30 Park Row, London SE10 9LS, UKComputational Science and Engineering Group, University of Greenwich, 30 Park Row, London SE10 9LS, UKThe use of a top-mounted electromagnetic induction coil has been demonstrated as a contactless alternative to traditional ultrasonic treatment (UST) techniques that use an immersed mechanical sonotrode for the treatment of metals in the liquid state. This method offers similar benefits to existing UST approaches, including degassing, grain refinement, and dispersion of nanoparticles, while also preventing contact contamination due to erosion of the sonotrode. Contactless treatment potentially extends UST to high temperature or reactive melts. Generally, the method relies on acoustic resonance to reach pressure levels suitable for inertial cavitation and as a result the active cavitation volume tends to lie deep in the melt rather than in the small volume surrounding the immersed sonotrode probe. Consequently, (i) with suitable tuning of the coil supply frequency for resonance, the treatment volume can be made arbitrarily large, (ii) the problem of shielding and pressure wave attenuation suffered by the immersed sonotrode is avoided. However, relying on acoustic resonance presents problems: (i) the emergence of bubbles alters the speed of sound, resonance is momentarily lost, and cavitation becomes intermittent, (ii) as sound waves travel through and reflect on all the materials surrounding the melt, the sound characteristics of the crucible and supporting structures need to be carefully considered. The physics of cavitation coupled with this intermittent behaviour poses a challenge to sonotrode modelling orthodoxy, a problem we are trying to address in this publication. Two alternative approaches will be discussed, one of which is in the time domain and one in the frequency domain, which couple the solution of a bubble dynamics solver with that of an acoustics solver, to give an accurate prediction of the acoustic pressure generated by the induction coil. The time domain solver uses a novel algorithm to improve simulation time, by detecting an imminent bubble collapse and prescribing its subsequent behaviour, rather than directly solving a region that would normally require extremely small time steps. This way, it is shown to predict intermittent cavitation. The frequency domain solver for the first time couples the nonlinear Helmholtz model used for studying cavitation, with a background source term for the contribution of Lorentz forces. It predicts comparable RMS pressures to the time domain solver, but not the intermittent behaviour due to the underlying harmonic assumption. As further validation, the frequency domain method is also used to compare the generated acoustic pressure with that of traditional UST using a mechanical sonotrode.http://www.sciencedirect.com/science/article/pii/S1350417722002346Ultrasonic melt processingNumerical modellingAcoustic cavitationAcoustic resonance |
| spellingShingle | Christopher Beckwith Georgi Djambazov Koulis Pericleous Catherine Tonry Comparison of frequency domain and time domain methods for the numerical simulation of contactless ultrasonic cavitation Ultrasonics Sonochemistry Ultrasonic melt processing Numerical modelling Acoustic cavitation Acoustic resonance |
| title | Comparison of frequency domain and time domain methods for the numerical simulation of contactless ultrasonic cavitation |
| title_full | Comparison of frequency domain and time domain methods for the numerical simulation of contactless ultrasonic cavitation |
| title_fullStr | Comparison of frequency domain and time domain methods for the numerical simulation of contactless ultrasonic cavitation |
| title_full_unstemmed | Comparison of frequency domain and time domain methods for the numerical simulation of contactless ultrasonic cavitation |
| title_short | Comparison of frequency domain and time domain methods for the numerical simulation of contactless ultrasonic cavitation |
| title_sort | comparison of frequency domain and time domain methods for the numerical simulation of contactless ultrasonic cavitation |
| topic | Ultrasonic melt processing Numerical modelling Acoustic cavitation Acoustic resonance |
| url | http://www.sciencedirect.com/science/article/pii/S1350417722002346 |
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