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

Authors :
Kahouadji, Lyes
Batchvarov, Assen
Amores, Cristian R. Constante
Shin, Seungwon
Chergui, Jalel
Juric, Damir
Craster, Richard V.
Matar, Omar K.
Publication Year :
2020

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.<br />Comment: rejected version

Subjects

Subjects :
Physics - Fluid Dynamics

Details

Database :
arXiv
Publication Type :
Report
Accession number :
edsarx.2011.08689
Document Type :
Working Paper