Viscous force exerted on a foam at a solid boundary: Influence of the liquid fraction and of the bubble size

Terriac, Emmanuel; Etrillard, J.; Cantat, Isabelle

doi:10.1209/epl/i2005-10583-2

Cited by 48 publications

(52 citation statements)

References 18 publications

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“…Hence, from our experimental observations we conclude that frictional effects at the boundaries have a negligible influence on the T1 dynamics. This result is not in contradiction with the observations made on the rheology of 2D foam [14,15,16], where a macroscopic stress (pressure drop) causes motion of the foam relative to the boundaries and the shear viscosity of the bulk solution is the main parameter controlling the dynamics.…”

contrasting

confidence: 54%

Relaxation Time of the TopologicalT1Process in a Two-Dimensional Foam

Durand

Stone²

2006

Phys. Rev. Lett.

128

112

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The elementary topological T1 process in a two-dimensional foam corresponds to the "flip" of one soap film with respect to the geometrical constraints. From a mechanical point of view, this T1 process is an elementary relaxation process through which the entire structure of an out-of-equilibrium foam evolves. The dynamics of this elementary relaxation process has been poorly investigated and is generally neglected during simulations of foams. We study both experimentally and theoretically the T1 dynamics in a dry two-dimensional foam. We show that the dynamics is controlled by the surface viscoelastic properties of the soap films (surface shear plus dilatational viscosity, µs + κ, and Gibbs elasticity ǫ), and is independent of the shear viscosity of the bulk liquid. Moreover, our approach illustrates that the dynamics of T1 relaxation process provides a convenient tool for measuring the surface rheological properties: we obtained ǫ = 32 ± 8 mN/m and µs + κ = 1.3 ± 0.7 mPa.m.s for SDS, and ǫ = 65 ± 12 mN/m and µs + κ = 31 ± 12 mPa.m.s for BSA, in good agreement with values reported in the literature.

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contrasting

confidence: 54%

Relaxation Time of the TopologicalT1Process in a Two-Dimensional Foam

Durand

Stone²

2006

Phys. Rev. Lett.

128

112

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“…An application of lubrication theory similar to ref. 33 to calculate the viscous forces within the wetting film on the wire yields the equation of motion D 2 _ D ∼ σh 2 ∕3μ, where h is a typical thickness of the film and μ is the fluid viscosity. This has the solution D ∼ ðσh 2 ∕μÞ 1∕3 ðt p − tÞ 1∕3 , an exponent consistent with the experimental value of ν 2 (Fig.…”

Section: Resultsmentioning

confidence: 99%

Soap-film Möbius strip changes topology with a twist singularity

Goldstein

Moffatt

Pesci

et al. 2010

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

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It is well-known that a soap film spanning a looped wire can have the topology of a Möbius strip and that deformations of the wire can induce a transformation to a two-sided film, but the process by which this transformation is achieved has remained unknown. Experimental studies presented here show that this process consists of a collapse of the film toward the boundary that produces a previously unrecognized finite-time twist singularity that changes the linking number of the film's Plateau border and the centerline of the wire. We conjecture that it is a general feature of this type of transition that the singularity always occurs at the surface boundary. The change in linking number is shown to be a consequence of a viscous reconnection of the Plateau border at the moment of the singularity. High-speed imaging of the collapse dynamics of the film's throat, similar to that of the central opening of a catenoid, reveals a crossover between two power laws. Far from the singularity, it is suggested that the collapse is controlled by dissipation within the fluid film surrounding the wire, whereas closer to the transition the power law has the classical form arising from a balance between air inertia and surface tension. Analytical and numerical studies of minimal surfaces and ruled surfaces are used to gain insight into the energetics underlying the transition and the twisted geometry in the neighborhood of the singularity. A number of challenging mathematical questions arising from these observations are posed.topological transition | contact line

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“…The surfactant Tween-20 (polyoxyethylene (20) sorbitan monolaurate) is non-ionic and has a molecular weight of 1228 g mol 21 and a CMC of 0.059 mM. The second surfactant we used, SDS, is anionic, and has a molecular weight of 288 g mol 21 and a CMC of 8.2 mM. We chose these two surfactants because one is charged and one non-ionic, and they are representative of typical chemical additives in lab-on-a-chip applications.…”

Section: The Experimental Designmentioning

confidence: 99%

The pressure drop along rectangular microchannels containing bubbles

et al. 2007

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This paper derives the difference in pressure between the beginning and the end of a rectangular microchannel through which a flowing liquid (water, with or without surfactant, and mixtures of water and glycerol) carries bubbles that contact all four walls of the channel. It uses an indirect method to derive the pressure in the channel. The pressure drop depends predominantly on the number of bubbles in the channel at both low and high concentrations of surfactant. At intermediate concentrations of surfactant, if the channel contains bubbles (of the same or different lengths), the total, aggregated length of the bubbles in the channel is the dominant contributor to the pressure drop. The difference between these two cases stems from increased flow of liquid through the ''gutters''-the regions of the system bounded by the curved body of the bubble and the corners of the channel-in the presence of intermediate concentrations of surfactant. This paper presents a systematic and quantitative investigation of the influence of surfactants on the flow of fluids in microchannels containing bubbles. It derives the contributions to the overall pressure drop from three regions of the channel: (i) the slugs of liquid between the bubbles (and separated from the bubbles), in which liquid flows as though no bubbles were present; (ii) the gutters along the corners of the microchannels; and (iii) the curved caps at the ends of the bubble.

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Viscous force exerted on a foam at a solid boundary: Influence of the liquid fraction and of the bubble size

Cited by 48 publications

References 18 publications

Relaxation Time of the TopologicalT1Process in a Two-Dimensional Foam

Relaxation Time of the TopologicalT1Process in a Two-Dimensional Foam

Soap-film Möbius strip changes topology with a twist singularity

The pressure drop along rectangular microchannels containing bubbles

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