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Mixing by bubble-induced turbulence

Alméras, Elise and Risso, Frédéric and Roig, Véronique and Cazin, Sébastien and Plais, Cécile and Augier, Frédéric Mixing by bubble-induced turbulence. (2015) Journal of Fluid Mechanics, 776. 458-474. ISSN 0022-1120

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Official URL: http://dx.doi.org/10.1017/jfm.2015.338

Abstract

This work reports an experimental investigation of the dispersion of a low-diffusive dye within a homogeneous swarm of high-Reynolds-number rising bubbles at gas volume fractions α ranging from 1% to 13 %. The capture and transport of dye within bubble wakes is found to be negligible and the mixing turns out to result from the bubble-induced turbulence. It is described well by a regular diffusion process. The diffusion coefficient corresponding to the vertical direction is larger than that corresponding to the horizontal direction, owing to the larger intensity of the liquid fluctuations in the vertical direction. Two regimes of diffusion have been identified. At low gas volume fraction, the diffusion time scale is given by the correlation time of the bubble-induced turbulence and the diffusion coefficients increase roughly as α 0.4. At large gas volume fraction, the diffusion time scale is imposed by the time interval between two bubbles and the diffusion coefficients become almost independent of α. The transition between the two regimes occurs sooner in the horizontal direction (1%6<α<63 %) than in the vertical direction (3%6<α<66 %). Physical models based on the hydrodynamic properties of the bubbleswarm are introduced and guidelines for practical applications are suggested.

Item Type:Article
Additional Information:Thanks to Cambridge University Press. The definitive version is available at http://journals.cambridge.org/ The original PDF of the article can be found at :http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9846212
Audience (journal):International peer-reviewed journal
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Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
French research institutions > IFP Energies Nouvelles - IFPEN (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
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Deposited On:20 Jun 2016 12:33

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