Hamburg 2001 – wissenschaftliches Programm
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DY: Dynamik und Statistische Physik
DY 52: Nichtlineare Dynamik II
DY 52.5: Vortrag
Freitag, 30. März 2001, 13:00–13:15, S 5.5
Response of rising bubbles to a sudden depressurization — •Claus-Dieter Ohl1 and Andrea Prosperetti1,2 — 1Department of Applied Physics, University of Twente, Enschede, The Netherlands — 2Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, U.S.A.
The response of single rising bubbles in a stagnant pressurized vertical tube filled with water is investigated experimentally. The bubble is subjected to a fast depressurization from a few atmospheres to ambient pressure. The translational and radial dynamics are recorded by means of high speed video and analyzed with digital image processing techniques. Depending on the rise velocity of the bubble (determined by the bubble size), and the magnification used, the bubble can be tracked for several hundred pictures and precise velocity data are obtained.
With this experiment the coupling between radial and translational dynamics of single bubbles is studied. Especially, the increase of the translational velocity for small rectilinearly rising bubbles is compared with a simple force balance model. The importance of added mass effects will be discussed. Additionally, this experiment allows to investigate the still puzzling phenomena of path instabilities occurring above a certain bubble radius.