Surfactant spreading on a thin liquid film: reconciling models and experiments

Swanson, Ellen R.; Strickland, Stephen L.; Shearer, Michael; Daniels, Karen E.

doi:10.1007/s10665-014-9735-0

Cited by 19 publications

(29 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The fluid ridge coalesces into a single central maximum and then relaxes to an equilibrium at the original uniform height (h(x, t) = 1). These general dynamics of fluid coalescence, central growth and decay were previously observed in laboratory experiments using laser profilometry [16,38,39], and are similar for either choice of EoS. However, there is an important distinction in h(x, t): for simulations run with the MEoS (Figure 3a,b and 4a,b) the annular fluid capillary ridge (double-peaked structure) coalesces more quickly than those with the EEoS.…”

Section: Inward Spreadingsupporting

confidence: 73%

“…For example, they are present in healthy lungs to enable breathing, and are also used in industrial 1 cm 1 cm 1 cm Figure 1. Images of fluorescently-tagged surfactant spreading from experiments [39,38] viewed from above; brighter regions have a larger concentration of surfactant. Left: inward-spreading below Γ c with laser line to show fluid profile with capillary ridges.…”

Section: Introductionmentioning

confidence: 99%

“…Right: outward spreading below Γ c with more uniform surfactant concentration. Figure adapted from [39,38].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Simulating surfactant spreading: Influence of a physically motivated equation of state

Sinclair¹,

Levy²,

Daniels³

2017

Eur. J. Appl. Math

Self Cite

View full text Add to dashboard Cite

In this paper, we present numerical simulations that demonstrate the effect of the particular choice of the equation of state (EoS) relating the surfactant concentration to the surface tension in surfactant-driven thin liquid films. Previous choices of the model EoS have been an ad-hoc decreasing function. Here, we instead propose an empirically motivated EoS; this provides a route to resolve some discrepancies and raises new issues to be pursued in future experiments. In addition, we test the influence of the choice of initial conditions and values for the non-dimensional groups. We demonstrate that the choice of EoS improves the agreement in surfactant distribution morphology between simulations and experiments, and influences the dynamics of the simulations. Because an empirically motivated EoS has regions with distinct gradients, future mathematical models may be improved by considering more than one timescale. We observe that the non-dimensional number controlling the relative importance of gravitational versus capillary forces has a larger influence on the dynamics than the other non-dimensional groups, but is nonetheless not a likely cause of discrepancy between simulations and experiments. Finally, we observe that the experimental approach using a ring to contain the surfactant could affect the surfactant and fluid dynamics if it disrupts the intended initial surfactant distribution. However, the fluid meniscus itself does not significantly affect the dynamics.

show abstract

Section: Inward Spreadingsupporting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Simulating surfactant spreading: Influence of a physically motivated equation of state

Sinclair¹,

Levy²,

Daniels³

2017

Eur. J. Appl. Math

Self Cite

View full text Add to dashboard Cite

show abstract

“…Hence, a lubrication approach for which the IPA is assumed to average quickly over the depth is not perfectly justified, but also the IPA does not remain perfectly at the interface. Similar to recent work on surfactants, 46 it would be interesting to further explore experimental possibilities to obtain more detailed information on the IPA distribution and the implications for the resulting Marangoni flow. We emphasize, however, that the results obtained here by experiment and scaling analysis capture the essential physical mechanisms.…”

Section: Discussionmentioning

confidence: 84%

Marangoni spreading due to a localized alcohol supply on a thin water film

2015

View full text Add to dashboard Cite

Bringing two miscible fluids into contact naturally generates strong gradients in surface tension. Here, we investigate such a Marangoni-driven flow by continuously supplying isopropyl alcohol (IPA) on a film of water, using micron-sized droplets of IPA-water mixtures. These droplets create a localized depression in surface tension that leads to the opening of a circular, thin region in the water film. At the edge of the thin region, there is a growing rim that collects the water of the film, reminiscent of Marangoni spreading due to locally deposited surfactants. In contrast to the surfactant case, the driving by IPA-water drops gives rise to a dynamics of the thin zone that is independent of the initial layer thickness. The radius grows as r ∼ t 1/2 , which can be explained from a balance between Marangoni and viscous stresses. We derive a scaling law that accurately predicts the influence of the IPA flux as well as the thickness of the thin film at the interior of the spreading front. C 2015 AIP Publishing LLC. [http://dx.

show abstract

“…A key advantage of these techniques is that they are non-invasive. Additionally, this and similar optical techniques (Vogel et al 2001;Fallest et al 2010;Strickland et al 2014;Swanson et al 2014) for measuring Γ depend upon the mean distance between the fluorophores and therefore are not affected by the dynamics of either molecular rearrangement or domain formation/relaxation. The container (black) is connected by low-friction air bushings to an electromagnetic shaker, and filled with a thin layer of water onto which a monolayer of NBD-PC surfactant is deposited.…”

Section: Introductionmentioning

confidence: 95%

Spatiotemporal measurement of surfactant distribution on gravity–capillary waves

2015

Self Cite

View full text Add to dashboard Cite

Materials adsorbed onto the surface of a fluid -for instance, crude oil, biogenic slicks or industrial/medical surfactants -will move in response to surface waves. Owing to the difficulty of non-invasive measurement of the spatial distribution of a molecular monolayer, little is known about the dynamics that couple the surface waves and the evolving density field. Here, we report measurements of the spatiotemporal dynamics of the density field of an insoluble surfactant driven by gravity-capillary waves in a shallow cylindrical container. Standing Faraday waves and travelling waves generated by the meniscus are superimposed to create a non-trivial surfactant density field. We measure both the height field of the surface using moiré imaging, and the density field of the surfactant via the fluorescence of NBD-tagged phosphatidylcholine, a lipid. Through phase averaging stroboscopically acquired images of the density field, we determine that the surfactant accumulates on the leading edge of the travelling meniscus waves and in the troughs of the standing Faraday waves. We fit the spatiotemporal variations in the two fields using an ansatz consisting of a superposition of Bessel functions, and report measurements of the wavenumbers and energy damping factors associated with the meniscus and Faraday waves, as well as the spatial and temporal phase shifts between them. While these measurements are largely consistent for both types of waves and both fields, it is notable that the damping factors for height and surfactant in the meniscus waves do not agree. This raises the possibility that there is a contribution from longitudinal waves in addition to the gravity-capillary waves.

show abstract

Surfactant spreading on a thin liquid film: reconciling models and experiments

Cited by 19 publications

References 37 publications

Simulating surfactant spreading: Influence of a physically motivated equation of state

Simulating surfactant spreading: Influence of a physically motivated equation of state

Marangoni spreading due to a localized alcohol supply on a thin water film

Spatiotemporal measurement of surfactant distribution on gravity–capillary waves

Contact Info

Product

Resources

About