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  • American Institute of Physics (AIP)  (2)
  • American Geophysical Union
  • Public Library of Science
  • 1990-1994  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    The influence of surfactant on the bubble motion in Hele–Shaw cells (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 3267-3275 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The surfactant influence on the bubble motion in a Hele–Shaw cell was studied experimentally. In order to differentiate the cases with and without the surfactant influence, the motion of air bubbles and water drops driven by silicone oil was investigated. The water drops contained a predetermined amount of an organic surfactant (sodium dodecyl sulfate), so that the dependence of their motion on the surfactant concentration could be studied systematically. In case of air bubbles in silicone oil, surfactants were likely to have negligible influence, although they might be present as contaminants, and their translational velocities were observed to be close to the prediction of Taylor and Saffman [Q. J. Mech. Appl. Math. 12, 265 (1959)]. The bubble shapes were also in accordance with available theories for a surfactant-free system. The water drops, on the other hand, behaved very differently, in that the translational velocities were smaller by an order of magnitude and their shapes were very unusual. These observations are apparently consistent with those of Kopf-Sill and Homsy [Phys. Fluids 31, 18 (1988)], and the present study suggests that the perplexing observations by them may be due to the influence of surface-active contaminants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868059
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of soluble surfactants on the motion of a finite bubble in a capillary tube (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2335-2347 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The steady motion of a long inviscid bubble displacing a viscous fluid in a capillary tube was first analyzed by Bretherton [J. Fluid Mech. 10, 166 (1961)] in the limit of small capillary number (Ca). While his theoretical prediction for the wetting film thickness left behind the moving front of the bubble showed good agreement with experimental observations for a moderately small Ca, it underpredicted the film thickness when Ca was smaller than about 10−4. In an attempt to resolve this discrepancy, several investigators studied the Marangoni effects of surface contaminants and predicted that the film thickness could be increased by a maximum factor of 42/3 if the surfactant transport is bulk-diffusion controlled. This prediction, however, is limited to the case of a semi-infinitely long bubble. The present study examines the motion of a finite length bubble in the presence of a small amount of surfactants. Both front and rear ends of the bubble are analyzed in the limit of small capillary number. The results indicate that due to the accumulation of the surfactant at the rear end of the bubble, the film thickening effect of the surfactant occurs only when the bubble length is larger than a certain critical value. It is also shown that the total pressure drop to drive the finite bubble through the capillary tube increases linearly with the length of the bubble as long as the bubble length is smaller than the critical value. When the bubble is longer than the critical value, the pressure drop does not increase any longer but remains to be constant. It appears that these results are capable of explaining the experimental observations of Schwartz and co-workers [J. Fluid Mech. 127, 259 (1986)] in which the film-thickening behavior at low Ca was shown to be dependent on the bubble length.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858475
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    Paper (German National Licenses)
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