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Approche multiéchelle de la dynamique des bulles en fluide non newtonien

Abstract : The hydrodynamics in a bubble column with non Newtonian fluids is a very complex problem. It is so even when the study is restricted to the case of a single bubble chain. Fluid's memory of long range, that governs bubbles' interactions and coalescences, leads usually to chaotic dynamics. A multiscale modelling approach has been realised to reach a convenient description of the complex system and to predict its global properties. Three different scales were considered: microscale, mesoscale and macroscale. Modelling results obtained at a scale are used as input to build the model of higher scale. ln such a way, Lattice Boltzmann (LB) simulation allows the computation of flow field, bubble shape and viscoelastic stress field, all in good agreement with experiments. A mesoscale model that takes into account the relationship between the bubble rise velocity and local stress encountered by the bubble is deduced from the LB approach. Finally, the cognitive model, that stems from the mesoscale results, gives the prediction of several macroscale properties in function of the column height: bubble number, bubble class distribution, route to chaos and mean bubble diameter. This pluridisciplinary theoretical modelling compares successfully with experimental data.
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Submitted on : Thursday, March 29, 2018 - 12:35:07 PM
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Xavier Frank. Approche multiéchelle de la dynamique des bulles en fluide non newtonien. Alimentation et Nutrition. Institut National Polytechnique de Lorraine, 2005. Français. ⟨NNT : 2005INPL099N⟩. ⟨tel-01749983⟩



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