Marangoni elasticity of flowing soap films

Kim, Ildoo; Mandre, Shreyas

doi:10.1103/physrevfluids.2.082001

Cited by 28 publications

(22 citation statements)

References 43 publications

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“…Therefore, even though the fluid is not compressed, we term the wave pattern "shock-like waves" in this present work. Similar shocklike waves have been observed as a wake structure on a liquid curtain behind an external perturbation (18) or an oblique liquid flow in a soap film (19). Then, the spreading drop is abruptly shattered/fragmented (Fig.…”

Section: Resultssupporting

confidence: 68%

How a raindrop gets shattered on biological surfaces

Kim

Esmaili

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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Many biological surfaces of animals and plants (e.g., bird feathers, insect wings, plant leaves, etc.) are superhydrophobic with rough surfaces at different length scales. Previous studies have focused on a simple drop-bouncing behavior on biological surfaces with low-speed impacts. However, we observed that an impacting drop at high speeds exhibits more complicated dynamics with unexpected shock-like patterns: Hundreds of shock-like waves are formed on the spreading drop, and the drop is then abruptly fragmented along with multiple nucleating holes. Such drop dynamics result in the rapid retraction of the spreading drop and thereby a more than twofold decrease in contact time. Our results may shed light on potential biological advantages of hypothermia risk reduction for endothermic animals and spore spreading enhancement for fungi via wave-induced drop fragmentation.

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Section: Resultssupporting

confidence: 68%

How a raindrop gets shattered on biological surfaces

Kim

Esmaili

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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“…This model finds confirmation when surface tension, measured at different values of the solution flux and at different concentrations, collapses onto a master curve. This observation also explains that the soap film's Marangoni elasticity measured using the angle of oblique Marangoni shocks (see title figure) does not vary with the film width, flow rate or soap concentration because the interface is saturated with soap (see Kim & Mandre 2017).…”

Section: Overviewmentioning

confidence: 61%

“…For instance, the pendant drop method requires bulk fluid and is therefore disqualified by default whereas other techniques such as the du Noüy and Wilhelmy plate methods are invasive and become especially problematic if the film flow speed exceeds the Marangoni wave speed (Kim & Mandre 2017). Sane et al (2018) circumvent all these difficulties by imaginatively exploiting the Euler-Bernoulli equation to relate the bending curvature of wires that bound the flowing film to its surface tension.…”

Section: Overviewmentioning

confidence: 99%

Tension grips the flow

Bandi¹

2018

J. Fluid Mech.

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Obstacle S h o c kBounding wire curved due to surface tension Flow Surface tension plays a dominant role in the formation and stability of soap films. It renders them both a quasi-two-dimensional fluid and an elastic membrane at the same time. The techniques for measuring the surface tension of the soap solution may very well apply to the static soap film, but how can the surface tension of a soap film be unintrusively measured, and what value would it assume? The answer, being at the intersection of physical chemistry, non-equilibrium physics and interfacial fluid dynamics, is not amenable to deduction via established methods. In a joint theoretical and experimental study, Sane et al. (J. Fluid Mech., vol. 841, 2018, R2) exploit elasticity theory to glean the answer through a simple, yet elegant framework.

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“…The experiments are carried out using an inclined soap film channel [16,19]. [20], indicating that the fluid medium is quasi two-dimensional.…”

Section: Methodsmentioning

confidence: 99%

Separated rows structure of vortex streets behind triangular objects

Kim

2019

J. Fluid Mech.

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We discuss two distinct spatial structures of vortex streets. The 'conventional mushroom' structure is commonly discuss in many experimental studies, but the exotic 'separated rows' structure is characterized by a thin irrotational fluid between two rows of vortices. In a two-dimensional soap film channel, we generated the exotic vortex arrangement by using triangular objects. This setup allows us to vary the thickness of boundary layers and their separation distance independently.We find that the separated rows structure appears only when the boundary layer thickness is less than 40% of the separation distance. We also discuss two physical mechanisms of the breakdown of vortex structures. The conventional mushroom structure decays due to the action of viscosity, and the separated rows structure decays because its arrangement is hydrodynamically unstable. arXiv:1807.00203v2 [physics.flu-dyn]

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Marangoni elasticity of flowing soap films

Cited by 28 publications

References 43 publications

How a raindrop gets shattered on biological surfaces

How a raindrop gets shattered on biological surfaces

Tension grips the flow

Separated rows structure of vortex streets behind triangular objects

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