0310305 - ÚCHP 2009 RIV SK eng C - Conference Paper (international conference)
Wichterle, K. - Raška, P. - Večeř, Marek
Bubbles Rising in Non-uniform Velocity Field.
[Stoupající bubliny v nestacionárním rychlostním poli.]
Proceedings. Bratislava: Slovak Society of Chemical Engineering, 2008 - (Markoš, J.), s. 311. ISBN 978-80-227-2903-1.
[35th International Conference of Slovak Society of Chemical Engineering. Tatranské Matliare (SK), 26.05.2008-30.05.2008]
R&D Projects: GA ČR GA104/07/1110
Institutional research plan: CEZ:AV0Z40720504
Keywords : bubbles * laminar shear flow
Subject RIV: CI - Industrial Chemistry, Chemical Engineering

Bubble rise in large volume of liquid is usually characterized by the mean rising velocity. After a short period just after the bubble formation, bubble becomes steady oscillation with frequency of oscillations 5-8 Hz. This oscillation is apparent mainly on the bubble wobbling, on either zig-zag or helical path, and also on variation of the rising velocity. We have developed theoretical model of forces responsible for the instability and periodical bubble movement. Here, the model is applied also to the case of bubble motion in steady laminar shear flow. Two different flow regimes belong to this situation. Smaller nearly spherical bubbles are rotating, which induces a side drift. Larger flat ellipsoidal bubbles oscillate about an inclined position which is responsible for a movement to the opposite side. According to the model, a rear bubble touching the wake region behind a leading bubble is drifted outside. Therefore, occurrence of a column of bubbles in train is less probable.

Vzestup bublin ve velkých objemech kapaliny je obvykle charakterizován střední vzestupnou rychlostí. Bubliny začnou oscilovat s frekvencí oscilace kolem 5-8Hz po velmi krátkém čase po jejich vytvoření. Tyto oscilace se projevují pohupováním bublin po jejich cik-cak či helikálních drahách a také na změnách vzestupné rychlosti. Představujeme model sil odpovědných za tuto nestabilitu a periodický pohyb bublin. V tomto případě je model rovněž aplikován na případ laminárního ustáleného smykového toku.

Permanent Link: http://hdl.handle.net/11104/0162216