Ripples on a rising bubble through an immiscible two-liquid interface generate numerous micro droplets

¹ Department of Mechanical Engineering, Kansai University - Osaka 564-8680, Japan
² Division of Materials Science and Engineering, Graduate School of Engineering, Hokkaido University Nishi 8, Kita 13, Kita-Ku, Sapporo, Hokkaido 060-8628, Japan

^a gaku@eng.hokudai.ac.jp

Received: 8 September 2010
Accepted: 14 October 2010

Abstract

The mass transfer between immiscible two liquid phases can be greatly accelerated by bubbling gas through a reactor (Bird R. B., Stewart W. E. and Lightfoot E. N., Transport Phenomena, 2nd edition (John Wiley and Sons) 2002). Therefore, the physical phenomenon occurring during the passage of a rising bubble through an immiscible two-liquid interface is of particular interest. The passage of the bubble through the oil (upper phase)/water (lower phase) interface starts with an upward lifting of the interface, and the bubble attracts a column of the water phase upwards keeping a film of the water phase around itself. In the present study, a particular remark is given to the influence of different interface tensions retracting the water film, after the water film ruptured, which lays on the interface between air and silicone oil. Unlike the previous studies on the rupture of a single liquid film in a gas which is pulled due to the identical surface tension, this system can form concentric ripples on the outer interface of the water film (oil/water interface) around the bubble due to the weak interface tension. Then, numerous micro water droplets break out from the fully grown ripples.