Effect of surfactant redistribution on the flow and stability of foam films
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Effect of surfactant redistribution on the flow and stability of foam films. / Vitasari, Denny; Grassia, Paul; Cox, Simon et al.
In: Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol. 476, No. 2234, 20190637, 26.02.2020.Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - Effect of surfactant redistribution on the flow and stability of foam films
AU - Vitasari, Denny
AU - Grassia, Paul
AU - Cox, Simon
AU - Rosario, Ruben
PY - 2020/2/26
Y1 - 2020/2/26
N2 - The viscous froth model for two-dimensional (2D) dissipative foam rheology is combined with Marangoni-driven surfactant redistribution on a foam film. The model is used to study the flow of a 2D foam system consisting of one bubble partially filling a constricted channel and a single spanning film connecting it to the opposite channel wall. Gradients of surface tension arising from film deformation induce tangential flow that redistributes surfactant along the film. This redistribution, and the consequent changes in film tension, inhibit the structure from undergoing a foam-destroying topological change in which the spanning film leaves the bubble behind; foam stability is thereby increased. The system's behaviour is categorized by a Gibbs-Marangoni parameter, representing the ratio between the rate of motion in tangential and normal directions. Larger values of the Gibbs-Marangoni parameter induce greater variation in surface tension, increase the rate of surfactant redistribution and reduce the likelihood of topological changes. An intermediate regime is, however, identified in which the Gibbs-Marangoni parameter is large enough to create a significant gradient of surface tension but is not great enough to smooth out the flow-induced redistribution of surfactant entirely, resulting in non-monotonic variation in the bubble height, and hence in foam stability.
AB - The viscous froth model for two-dimensional (2D) dissipative foam rheology is combined with Marangoni-driven surfactant redistribution on a foam film. The model is used to study the flow of a 2D foam system consisting of one bubble partially filling a constricted channel and a single spanning film connecting it to the opposite channel wall. Gradients of surface tension arising from film deformation induce tangential flow that redistributes surfactant along the film. This redistribution, and the consequent changes in film tension, inhibit the structure from undergoing a foam-destroying topological change in which the spanning film leaves the bubble behind; foam stability is thereby increased. The system's behaviour is categorized by a Gibbs-Marangoni parameter, representing the ratio between the rate of motion in tangential and normal directions. Larger values of the Gibbs-Marangoni parameter induce greater variation in surface tension, increase the rate of surfactant redistribution and reduce the likelihood of topological changes. An intermediate regime is, however, identified in which the Gibbs-Marangoni parameter is large enough to create a significant gradient of surface tension but is not great enough to smooth out the flow-induced redistribution of surfactant entirely, resulting in non-monotonic variation in the bubble height, and hence in foam stability.
KW - viscous froth
KW - Marangoni effect
KW - foam flow
KW - microfluidic channel
KW - MODEL
U2 - 10.1098/rspa.2019.0637
DO - 10.1098/rspa.2019.0637
M3 - Article
C2 - 32201478
VL - 476
JO - Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
JF - Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
SN - 0080-4630
IS - 2234
M1 - 20190637
ER -