Instability and symmetry breaking in binary evaporating thin films over a solid spherical dome

Shi, Xingyi; Rodríguez-Hakim, Mariana; Shaqfeh, Eric S. G.; Fuller, Gerald G.

doi:10.1017/jfm.2021.136

Cited by 7 publications

(3 citation statements)

References 28 publications

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“…Similar to our previous study (Shi et al. 2021), the base state evolves in time and in the radial direction. The linearized stability equations are derived by subtracting the axisymmetric, 1-D governing equations from the 2-D governing equations described in the theory section, followed by discarding all nonlinear terms in the disturbance quantities, , where represents , , , , and .…”

Section: Resultssupporting

confidence: 85%

“…Additional experimental examples of asymmetrical dynamic evolution of thin films are discussed in our previous work (Shi et al. 2021).…”

Section: Introductionmentioning

confidence: 94%

“…As will be shown in the results section, the model is only used to capture the dynamics during the onset of the disturbance. During this time, the minimum film thickness is around 200 nm, thus, we neglect the effects of the disjoining pressure (Stubenrauch & Von Klitzing 2003).…”

Section: Lubrication Equationsmentioning

confidence: 99%

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Instability and symmetry breaking of surfactant films over an air bubble

2022

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We examine the asymmetric flows of aqueous surfactant films over an air bubble. A thin film is formed by raising an equilibrated air bubble through an aqueous solution of Triton X-100 (0.01 mM, below critical micelle concentration). Due to the advection generated by the squeezing motion, the initially uniformly distributed surfactants redistribute and, thus, generate an axisymmetric surface tension gradient that drives a Marangoni flow. The external forcing of raising the bubble also creates an axisymmetric dimpled film with a radial thickness variation that reaches its minimum at the rim of the dimple. The curvature in the film thickness generates an axisymmetric capillary pressure driven flow. When the apex of the bubble has penetrated the initially flat air-solution interface, the rising bubble is stopped and the resulting flow demonstrates symmetry breaking both in the experiment and in the parameter matched numerical simulation. Linear stability analysis reveals the mechanism behind the disturbance growth. It is found that the most dangerous azimuthal wavenumber scales linearly with the ratio of the rim radius to the radial width of significant radial pressure and surface tension gradients after stopping the bubble. Finally, we compare this instability to the previously studied surfactant spreading induced fingering phenomenon (Warner, Craster & Matar, Phys. Fluids, vol. 16, issue 8, 2004, pp. 2933–2951).

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Section: Resultssupporting

confidence: 85%

“…Additional experimental examples of asymmetrical dynamic evolution of thin films are discussed in our previous work (Shi et al. 2021).…”

Section: Introductionmentioning

confidence: 94%

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Instability and symmetry breaking of surfactant films over an air bubble

2022

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On modeling tear breakup dynamics with a nematic lipid layer

Taranchuk,

Braun

2024

J Eng Math

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One of the main roles of the lipid layer (LL) of the tear film (TF) is to help prevent evaporation of the aqueous layer (AL). The LL thickness, composition, and structure all contribute to its barrier function. It is believed that the lipid layer is primarily nonpolar with a layer of polar lipids at the LL/AL interface. There is evidence that the nonpolar region of the LL may have liquid crystalline characteristics. We investigate the structure and function of the LL via a model of the tear film with two layers, using extensional flow of a nematic liquid crystal for the LL and shear-dominated flow of a Newtonian AL. Evaporation is taken into account and is affected by the LL thickness, internal arrangement of its rod-like molecules, and external conditions. We conduct a detailed parameter study with a focus on the evaporative resistance parameter, the Marangoni number, and primary liquid crystal parameters including the Leslie viscosities and director angle. This new model responds similarly to previous Newtonian models in some respects; however, incorporating internal structure via the orientation of the liquid crystal molecules affects both evaporation and flow. As a result, we see new effects on TF dynamics and breakup.

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