Comparison of frequency domain and time domain methods for the numerical simulation of contactless ultrasonic cavitation.
Comparison of frequency domain and time domain methods for the numerical simulation of contactless ultrasonic cavitation.
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DOI：
10.1016/j.ultsonch.2022.106138
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发表时间：
2022-09
影响因子：
8.4
通讯作者：
Tonry, Catherine
中科院分区：
文献类型：
--
作者：
Beckwith, Christopher;Djambazov, Georgi;Pericleous, Koulis;Tonry, Catherine
开发了一种新的算法来提高时间域声空化模拟的计算效率。将频域声空化模型耦合到背景电磁解算器，用于模拟液态铝的非接触式超声波处理。这两种方法得到了相似的结果，但用频域求解器获得的声压略低，这可能是由于只存在于时间相关求解器中的更高频率的谐波的影响。这两种方法都表明，非接触式交流感应线圈可以通过共振达到声空化的布莱克阈值，但空化气泡的衰减会阻止进一步的共振，并导致间歇性空化。使用顶部安装的电磁感应线圈已被证明是传统超声波处理(UST)技术的非接触式替代技术，传统超声处理技术使用浸没的机械声电极来处理液态金属。这种方法提供了与现有的UST方法类似的好处，包括脱气、颗粒细化和纳米颗粒的分散，同时还防止了由于声电极的侵蚀而造成的接触污染。非接触式处理可能会将UST扩展到高温或活性熔体。通常，该方法依靠声共振达到适合惯性空化的压力水平，因此，活跃的空化体积往往位于熔体的深处，而不是浸入声电极探头周围的小体积。因此，(I)通过适当地调节用于谐振的线圈供应频率，可以使处理体积任意大，(Ii)避免了浸入声电极所遇到的屏蔽和压力波衰减的问题。然而，依靠声学共振会带来问题：(1)气泡的出现改变了声速，共振暂时丧失，空化成为间歇性的；(2)当声波穿过熔体周围的所有材料并在其上反射时，需要仔细考虑坩埚和支撑结构的声音特性。空化的物理学加上这种间歇性的行为对声道建模的正统理论提出了挑战，这是我们试图在本出版物中解决的问题。将讨论两种替代方法，一种在时间域中，另一种在频域中，这两种方法将气泡动力学解算器的解与声学解算器的解相耦合，以给出感应线圈产生的声压的准确预测。时间域解算器使用一种新的算法来改进模拟时间，通过检测即将到来的气泡崩溃并规定其后续行为，而不是直接求解通常需要极小时间步长的区域。这样，它被证明可以预测间歇性空化。频域解算器首次将用于研究空化的非线性Helmholtz模型与用于洛伦兹力贡献的背景源项相结合。它预测了与时间域解算器类似的均方根压力，但不能预测由于潜在的谐波假设而产生的间歇性行为。作为进一步的验证，还使用频域方法比较了使用机械声纳电极产生的声压与传统UST产生的声压。
Development of a novel algorithm for improving the computational efficiency of time domain acoustic cavitation simulation. Coupling of a frequency domain acoustic cavitation model to a background Electromagnetics solver for the simulation of contactless ultrasonic processing of liquid aluminium. Both methods achieve similar results, but acoustic pressures obtained with the frequency domain solver are slightly lower, potentially due to influence from higher frequency harmonics which only exist in the time dependent solver. Both methods show that a contactless AC induction coil can reach the Blake threshold for acoustic cavitation through resonance, but attenuation due to cavitating bubbles then prevents further resonance and results in intermittent 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 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.
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影响因子：
64.8
作者：
Flannigan, DJ;Suslick, KS
通讯作者：
Suslick, KS
影响因子：
8.4
作者：
Lebon, G. S. Bruno;Tzanakis, Iakovos;Eskin, Dmitry
通讯作者：
Eskin, Dmitry
DOI：
10.1063/1.858700
发表时间：
1993-11-01
期刊：
PHYSICS OF FLUIDS A-FLUID DYNAMICS
影响因子：
--
作者：
LOFSTEDT, R;BARBER, BP;PUTTERMAN, SJ
通讯作者：
PUTTERMAN, SJ
影响因子：
2.4
作者：
COMMANDER, KW;PROSPERETTI, A
通讯作者：
PROSPERETTI, A
影响因子：
2.4
作者：
KELLER, JB;MIKSIS, M
通讯作者：
MIKSIS, M