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Investigations on the Stability of the Flow Characteristics in a Bubble Column
Author(s) -
Lucas D.,
Krepper E.,
Prasser H.M.,
Manera A.
Publication year - 2006
Publication title -
chemical engineering and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.403
H-Index - 81
eISSN - 1521-4125
pISSN - 0930-7516
DOI - 10.1002/ceat.200600150
Subject(s) - bubble , mechanics , lift (data mining) , homogeneous , flow (mathematics) , stability (learning theory) , computational fluid dynamics , materials science , chemistry , thermodynamics , physics , machine learning , computer science , data mining
Abstract The role of the lift force in the stability of the homogeneous flow regime in a bubble column is investigated. Instabilities caused by the lift force may be one important reason for the transition from a homogeneous to a heterogeneous bubble column. The lift force acts on rising bubbles in a lateral direction when gradients of the liquid velocity are present. Such gradients may result from circulation cells in the bubble column as well as from local disturbances. Depending on the sign of the lift force, such local disturbances in a homogeneous flow may be damped or enhanced. The corresponding feedback mechanism was analyzed by means of linear stability analyses. As a result, criteria for stability were obtained for mono‐dispersed flow, for a flow with two bubble size groups, and, finally, with some additional approximations also for the case of N bubble size groups or a given bubble size distribution. In a next step, the effects were investigated by CFD calculations. The obtained criteria for stability fit well with the observed effects in CFD simulations. Recently, two different groups confirmed the stability criteria experimentally.