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Mixing mechanisms in a low-sheared inhomogeneous bubble column

Alméras, Élise and Plais, Cécile and Roig, Véronique and Risso, Frédéric and Augier, Frédéric Mixing mechanisms in a low-sheared inhomogeneous bubble column. (2018) Chemical Engineering Science, 186. 52-61. ISSN 0009-2509

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Official URL: https://doi.org/10.1016/j.ces.2018.04.026

Abstract

This paper reports an experimental study of the mixing of a passive scalar in a bubble column at high Reynolds number and average gas volume fractions ranging from 2.0% to 7.5%. Starting from a homogeneous bubble column, the bubbly flow is progressively destabilized by imposing a gradient of gas volume fraction at the bottom of the tank. In that way, a single recirculation is produced, which allows to investigate the impact of a large-scale buoyancy-driven flow on the mixing of a passive scalar. It is shown that, as long as the shear-induced turbulence generated by the recirculation is negligible, mixing results from two main mixing mechanisms: the transport by the mean liquid velocity and the mixing induced by the bubbles. While the transport by the liquid recirculation can be accounted for by an advection term, the mixing induced by the bubbles is a diffusive process, the effective diffusivity of which has been measured in a homogeneous bubble column by Alméras et al. (2015). However, once the shear-induced turbulence produced by the shear develops, its role upon the mixing has to be taken into account too.

Item Type:Article
Additional Information:This is an open access article under the CC BY-NC-ND license : https://creativecommons.org/licenses/by-nc-nd/4.0/. Thanks to Elsevier editor. The definitive version of this document is available at: https://www.sciencedirect.com/science/article/pii/S0009250918302318?via%3Dihub
HAL Id:hal-01989148
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT (FRANCE)
French research institutions > IFP Energies Nouvelles - IFPEN (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UPS (FRANCE)
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Deposited By: Frederic RISSO
Deposited On:26 Feb 2019 11:17

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