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Effect of bubble’s arrangement on the viscous torque in bubbly Taylor-Couette flow

Ndongo Fokoua, Georges and Gabillet, Céline and Aubert, Adrien and Colin, Catherine Effect of bubble’s arrangement on the viscous torque in bubbly Taylor-Couette flow. (2015) Physics of Fluids, 27. 034105/1- 034105/32. ISSN 1070-6631

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Official URL: http://dx.doi.org/10.1063/1.4915071

Abstract

An experimental investigation of the interactions between bubbles, coherent motion and viscous drag in a Taylor-Couette flow with the outer cylinder at rest is presented. The cylinder radii ratio η is 0.91. Bubbles are injected inside the gap through a needle at the bottom of the apparatus. Different bubbles sizes are investigated (ratio between the bubble diameter and the gap width ranges from 0.05 to 0.125) for very small void fraction (α≤0.23%). Different flow regimes are studied corresponding to Reynolds number Re based on the gap width and velocity of the inner cylinder, ranging from 6.102 to 2.104. Regarding these Re values, Taylor vortices are persistent leading to an axial periodicity of the flow. A detailed characterization of the vortices is performed for the single-phase flow. The experiment also develops bubbles tracking in a meridian plane and viscous torque of the inner cylinder measurements. The findings of this study show evidence of the link between bubbles localisation, Taylor vortices and viscous torque modifications. We also highlight two regimes of viscous torque modification and various types of bubbles arrangements, depending on their size and on the Reynolds number. Bubbles can have a sliding and wavering motion near the inner cylinder and be either captured by the Taylor vortices or by the outflow areas near the inner cylinder. For small buoyancy effect, bubbles are trapped, leading to an increase of the viscous torque. When buoyancy induced bubbles motion is increased by comparison to the coherent motion of the liquid, a decrease in the viscous torque is rather observed. The type of bubble arrangement is parameterized by the two dimensionless parameters C and H introduced by Climent et al. [E. Climent, M. Simonnet and J. Magnaudet, Phys. Fluids 19, 083301(2007)]. Phase diagrams summarizing the various types of bubbles arrangements, viscous torque modifications and axial wavelength evolution are built.

Item Type:Article
Additional Information:Thanks to AIP Publishing . The definitive version is available at http://scitation.aip.org/ The original PDF of the article can be found at: http://scitation.aip.org/content/aip/journal/pof2/27/3/10.1063/1.4915071
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Other partners > Ecole Navale (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UPS (FRANCE)
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Deposited By: Catherine COLIN
Deposited On:01 Jul 2016 08:49

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