Please use this identifier to cite or link to this item:
|Title:||Experiments on bubble pinch-off|
|Authors:||Thoroddsen, S.T. |
|Source:||Thoroddsen, S.T., Etoh, T.G., Takehara, K. (2007-04). Experiments on bubble pinch-off. Physics of Fluids 19 (4) : -. ScholarBank@NUS Repository. https://doi.org/10.1063/1.2710269|
|Abstract:||A bubble is slowly grown from a vertical nozzle until it becomes unstable and pinches off. We use ultra-high-speed video imaging, at frame-rates up to 1millionfps, to study the dynamics and shape of the pinch-off neck region. For bubbles in water (Bo ≃ 1.0) the radius of the neck reduces with a power law behavior R∼tα, over more than 2 decades, with an exponent in the range α=0.57 ± 0.03, in good agreement with other available studies, but which is slightly larger than 1/2 predicted by Rayleigh-Plesset theory. The vertical curvature in the neck increases more slowly than the azimuthal curvature, making the neck profiles more slender as pinch-off is approached. Self-similar shapes are recovered by normalizing the axial coordinate by a separate length scale which follows a different power law, Lz∼tγ, where γ=0.49 ± 0.03. Results for air, He, and SF6 gas are identical, suggesting that the gas density plays a minimal role in the dynamics. The pinch-off in water leaves behind a tiny satellite bubble, around 5 uml;m in diameter and the flow-field inside the liquid is shown to be consistent with simple sink flow. The effects of liquid viscosity on the pinch-off speed and neck shapes, are also characterized. The speed starts to slow down at a viscosity of about 10 times that of water, which corresponds to Reμ ≃ 2000. This also changes the power law, increasing the exponent to α ≃ 1 for viscosities above 70cP (Reμ ≃ 40). For surrounding liquid of viscosity above 10cP, we observe just before pinch-off, that the neck is stretched into a thin filament of air, which then breaks into a stream of microbubbles. In some cases we observe a cascade of bubble sizes. While some of the details differ, our results are in overall agreement with those of Burton, Waldrep, and Taborek [Phys. Rev. Lett. 94, 184502 (2005)], except we do not observe the rupture of the air cylinder as it reduces to 50 μm size. For water we observe a continuous necking down to the pixel-resolution of our optical system, which at the largest frame-rates is ∼10 μm. © 2007 American Institute of Physics.|
|Source Title:||Physics of Fluids|
|Appears in Collections:||Staff Publications|
Show full item record
Files in This Item:
There are no files associated with this item.
checked on Feb 21, 2018
WEB OF SCIENCETM
checked on Jan 17, 2018
checked on Feb 19, 2018
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.