期刊
ULTRASONICS SONOCHEMISTRY
卷 19, 期 1, 页码 56-65出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.ultsonch.2011.06.007
关键词
Acoustic cavitation; Bubble dynamics; Propagation in bubbly liquids; Wave attenuation
资金
- French Agence Nationale de la Recherche (ANR) Controle par ultrasons de la nucleation de la glace pour l'optimisation des procedes de congelation et de lyophilisation [ANR-09-BLAN-0040-02]
- Agence Nationale de la Recherche (ANR) [ANR-09-BLAN-0040] Funding Source: Agence Nationale de la Recherche (ANR)
The bubbles involved in sonochemistry and other applications of cavitation oscillate inertially. A correct estimation of the wave attenuation in such bubbly media requires a realistic estimation of the power dissipated by the oscillation of each bubble, by thermal diffusion in the gas and viscous friction in the liquid. Both quantities and calculated numerically for a single inertial bubble driven at 20 kHz, and are found to be several orders of magnitude larger than the linear prediction. Viscous dissipation is found to be the predominant cause of energy loss for bubbles small enough. Then, the classical nonlinear Catfish equations describing the propagation of acoustic waves in a bubbly liquid are recast and simplified conveniently. The main harmonic part of the sound field is found to fulfill a nonlinear Helmholtz equation, where the imaginary part of the squared wave number is directly correlated with the energy lost by a single bubble. For low acoustic driving, linear theory is recovered, but for larger drivings, namely above the Blake threshold, the attenuation coefficient is found to be more than 3 orders of magnitude larger then the linear prediction. A huge attenuation of the wave is thus expected in regions where inertial bubbles are present, which is confirmed by numerical simulations of the nonlinear Helmholtz equation in a 1D standing wave configuration. The expected strong attenuation is not only observed but furthermore, the examination of the phase between the pressure field and its gradient clearly demonstrates that a traveling wave appears in the medium. (C) 2011 Elsevier B.V. All rights reserved.
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