Instabilities at a sheared interface over a liquid laden with soluble surfactant

Kalogirou, Anna; Blyth, Mark

doi:10.1007/s10665-021-10140-4

Cited by 2 publications

(2 citation statements)

References 27 publications

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“…This indicates that the effect of interfacial diffusion is negligible in comparison to bulk diffusion. A similar assumption can also be found in previous literature (Kalogirou & Blyth 2019, 2021). Term Im() of the interface mode also increases with increasing bulk diffusivity, i.e.…”

Section: The Long-wave Approximation Analysissupporting

confidence: 88%

“…(2020) considered both the solutocapillary effect of soluble surfactant and the thermocapillary effect, and reached the same conclusion. Kalogirou & Blyth (2019, 2020, 2021) investigated a two-layer shear flow with soluble surfactant dissolving in the lower layer. They reported that solubility and sorption kinetics could influence interfacial dynamics and the effect of soluble surfactant on the instability could be either stabilizing or destabilizing.…”

Section: Introductionmentioning

confidence: 99%

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The role of soluble surfactant in the linear instability of a film coating inside a tube

Li,

Chen,

Cheng

et al. 2023

J. Fluid Mech.

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This study investigates the linear instability of a thin-film coating inside a rigid tube. The flow is assumed to be inertialess and driven by an axial body force (e.g. gravity), an interfacial shearing force, or their combinations. The interface and the bulk of the film are laden with soluble surfactant. The properties of the soluble surfactant, i.e. solubility, sorption kinetics and bulk diffusivity, modulate the interfacial dynamics of the film. The influence of these properties on the linear instability of the film is comprehensively investigated via long-wave approximation analysis and numerical calculation. Two modes, namely the interface mode and the surfactant mode, are identified to dominate the instability. For a quiescent film, it is found that solubility, sorption kinetics and bulk diffusivity act to improve the uniformity of the surface surfactant and mitigate the stabilizing effect of the Marangoni force. For the film driven by the axial body/interfacial shearing force, the results reveal that solubility plays contrasting roles in the interface mode and the surfactant mode. A window with intermediate solubility is detected where the film can be linearly stabilized. Moreover, sorption kinetics is found to destabilize the perturbations with long wavelength whereas it stabilizes the perturbations with finite wavelength. The bulk diffusivity of the surfactant has a non-monotonic influence on the flow instability, and the film can be relatively stable at both strong and weak diffusivity.

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Section: The Long-wave Approximation Analysissupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

The role of soluble surfactant in the linear instability of a film coating inside a tube

Li,

Chen,

Cheng

et al. 2023

J. Fluid Mech.

View full text Add to dashboard Cite

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Electrohydrodynamic stability of a two-layer plane Poiseuille flow in the presence of interfacial surfactant: Energy budget analysis

Yadav,

Chattopadhyay

2024

Physics of Fluids

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The electrohydrodynamic stability of a two-layer plane Poiseuille flow has been examined under the influence of an electric field acting normally to the unperturbed interface of two viscous immiscible fluids. The presence of insoluble surfactant at the interface is considered to achieve passive control over the instability that naturally comes into play in such flows. The fluids considered here for the asymptotic and numerical stability analyses are treated as leaky dielectrics, which are allowed to have different viscosities, densities, permittivities, and conductivities. An asymptotic analysis shows that the two opposite influences from the electrical stresses and the Marangoni stresses in competition at the interface give rise to remarkably different patterns of neutral curves depending upon the ratios of viscosities and thicknesses of the fluid layers. A linear stability analysis utilizing the Chebyshev spectral collocation method for disturbances of all wave numbers is employed numerically to obtain various types of dispersion curves and neutral stability diagrams originating from the associated Orr–Sommerfeld eigenvalue problem. Our results suggest that increasing the electrical conductivity ratio leads to an increase in the growth rate of disturbances, whereas an increase in the electrical permittivity ratio stabilizes the flow as the interfacial surface tension resists the growth of perturbations that are otherwise promoted by electrical stresses. The energy budget calculations show that the presence of the insoluble surfactant is primarily responsible for the viscosity-induced instability triggered by the modified interface deformation. The comparisons with pertinent studies are performed to enhance the quantitative reliability of the present work.

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Instabilities at a sheared interface over a liquid laden with soluble surfactant

Cited by 2 publications

References 27 publications

The role of soluble surfactant in the linear instability of a film coating inside a tube

The role of soluble surfactant in the linear instability of a film coating inside a tube

Electrohydrodynamic stability of a two-layer plane Poiseuille flow in the presence of interfacial surfactant: Energy budget analysis

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