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Shape oscillations of an oil drop rising in water: effect of surface contamination

Abi Chebel, Nicolas and Vejražka, Jiří and Masbernat, Olivier and Risso, Frédéric Shape oscillations of an oil drop rising in water: effect of surface contamination. (2012) Journal of Fluid Mechanics, vol. 702. pp. 533-542. ISSN 0022-1120

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Official URL: http://dx.doi.org/10.1017/jfm.2012.205

Abstract

Inertial shape oscillations of heptane drops rising in water are investigated experimentally. Diameters from 0.59 to 3.52 mm are considered, corresponding to a regime where the rising motion should not affect shape oscillations for pure immiscible fluids. The interface, however, turns out to be contaminated. The drag coefficient is considerably increased compared to that of a clean drop due to the well-known. Marangoni effect resulting from a gradient of surfactant concentration generated by the fluid motion along the interface. Thanks to the decomposition of the shape into spherical harmonics, the eigenfrequencies and the damping rates of oscillation modes n = 2, 3, 4 and 5 have been measured. Frequencies are not affected by contamination, while damping rates are increased by a considerable amount that depends neither on drop instantaneous velocity nor on diameter. This augmentation, however, depends on the mode number: it is maximum for mode two (multiplied by 2.4) and then relaxes towards the value of a clean drop as n increases. A previous similar investigation of a drop attached to a capillary has not revealed such an increase of the damping rates, indicating that the coupling between rising motion and surface contamination is responsible for this effect.

Item Type:Article
HAL Id:hal-00906149
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:Other partners > Academy of Sciences (CZECH REPUBLIC)
French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT (FRANCE)
Université de Toulouse > Institut National des Sciences Appliquées de Toulouse - INSA (FRANCE)
French research institutions > IFP Energies Nouvelles - IFPEN (FRANCE)
Université de Toulouse > Université Paul Sabatier-Toulouse III - UPS (FRANCE)
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Deposited By: Vincent GERBAUD
Deposited On:13 Nov 2013 12:22

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