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Journal Articles FLOW Year : 2022

The transition to aeration in two-phase mixing in stirred vessels

Abstract

We consider the mixing of a viscous fluid by the rotation of a pitched blade turbine inside an open, cylindrical tank, with air as the lighter fluid above. To examine the flow and interfacial dynamics, we utilise a highly-parallelised implementation of a hybrid front-tracking/level-set method that employs a domain-decomposition parallelisation strategy. Our numerical technique is designed to capture faithfully complex interfacial deformation, and changes of topology, including interface rupture and dispersed phase coalescence. As shown via transient, three-dimensional direct numerical simulations, the impeller induces the formation of primary vortices that arise in many idealised rotating flows as well as several secondary vortical structures resembling Kelvin-Helmholtz, vortex breakdown, blade tip vortices, and end-wall corner vortices. As the rotation rate increases, a transition to 'aeration' is observed when the interface reaches the rotating blades leading to the entrainment of air bubbles into the viscous fluid and the creation of a bubbly, rotating, free surface flow. The mechanisms underlying the aeration transition are probed as are the routes leading to it, which are shown to exhibit a strong dependence on flow history.
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Dates and versions

hal-02994847 , version 2 (08-11-2020)
hal-02994847 , version 1 (13-09-2022)

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Lyes Kahouadji, Fuyue Liang, Juan Valdes, Seungwon Shin, Jalel Chergui, et al.. The transition to aeration in two-phase mixing in stirred vessels. FLOW, 2022, 2, pp.E30. ⟨10.1017/flo.2022.24⟩. ⟨hal-02994847v2⟩
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