Rheological properties of the soft-disk model of two-dimensional foams

Langlois, Vincent; Hutzler, Stefan; Weaire, D.

doi:10.1103/physreve.78.021401

Cited by 61 publications

(82 citation statements)

References 33 publications

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“…For example, the values of the flow indexes and the character of shear-localization phenomena were shown to be affected strongly by the covering solid wall (present in most of the experiments with 2D-foams) which creates additional bubble-wall friction force without direct analog in 3D-foams. [76][77][78][79][80] Even when the solid wall is absent, the measured flow indexes are often different from those measured with 3D-foams of the same surfactants (for example, cf. the results with Dawn presented in section 5.3 below to those presented in ref.…”

Section: Steadily Sheared 2d-foams the Role Of Foam Polydispersity mentioning

confidence: 99%

“…79,81 On this basis, a hypothesis was put forward that these results should be representative for the typical polydisperse foams. [76][77][78]81 To clarify the role of bubble polydispersity in foam viscous friction, we performed additional experiments with monodisperse 3D-foams. In Fig.…”

Section: -78mentioning

confidence: 99%

“…[76][77][78][79][80][81][93][94][95][96][97][98][99][100] These experiments proved to be very valuable in analyzing several important phenomena (e.g., those related to non-homogeneous flows) and to clarify some common features of the different types of ''yield stress systems'', such as soft glassy materials, granular materials, foams, and emulsions. Also, the theoretical modelling of 2D-foams is technically much simpler, as compared to the 3D-foams, so that the theoretical concepts could be more easily tested with 2D-foams.…”

Section: Steadily Sheared 2d-foams the Role Of Foam Polydispersity mentioning

confidence: 99%

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The role of surfactant type and bubble surface mobility in foam rheology

et al. 2009

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This paper is an overview of our recent understanding of the effects of surfactant type and bubble surface mobility on foam rheological properties. The focus is on the viscous friction between bubbles in steadily sheared foams, as well as between bubbles and confining solid wall. Large set of experimental results is reviewed to demonstrate that two qualitatively different classes of surfactants can be clearly distinguished. The first class is represented by the typical synthetic surfactants (such as sodium dodecylsulfate) which are characterised with low surface modulus and fast relaxation of the surface tension after a rapid change of surface area. In contrast, the second class of surfactants exhibits high surface modulus and relatively slow relaxation of the surface tension. Typical examples for this class are the sodium and potassium salts of fatty acids (alkylcarboxylic acids), such as lauric and myristic acids. With respect to foam rheology, the second class of surfactants leads to significantly higher viscous stress and to different scaling laws of the shear stress vs. shear rate in flowing foams. The reasons for these differences are discussed from the viewpoint of the mechanisms of viscous dissipation of energy in sheared foams and the respective theoretical models. The process of bubble breakup in sheared foams (determining the final bubble-size distribution after foam shearing) is also discussed, because the experimental results and their analysis show that this phenomenon is controlled by foam rheological properties.

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Section: Steadily Sheared 2d-foams the Role Of Foam Polydispersity mentioning

confidence: 99%

Section: -78mentioning

confidence: 99%

Section: Steadily Sheared 2d-foams the Role Of Foam Polydispersity mentioning

confidence: 99%

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The role of surfactant type and bubble surface mobility in foam rheology

et al. 2009

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“…The 2D foam, as described by the bubble model (Durian, 1995;Langlois et al, 2008), is a dense packing of circular bubbles. A small polydispersity in bubble size is introduced to prevent crystallization of the bubbles, with each 70 bubble radius R i being chosen within a uniform distribution bounded by R 0 × (1 ± 0.2), R 0 being the average radius.…”

Section: Bubble Modelmentioning

confidence: 99%

“…This so-called bubble model, or soft-sphere model was introduced by Durian (1995) in order 50 to simulate mechanical properties of wet foams. As shown by Langlois et al (2008), this simplistic but computationally efficient approach is sufficient to reproduce the basic features of the rheology of foams: existence of a yield stress, Herschel-Bulkley shear-thinning rheology, occurrence of shear-bands in a HeleShaw cell, and it can also be appropriate for more complex geometries (Langlois,55 2014).…”

Section: Introductionmentioning

confidence: 99%

Dynamics of a flexible fibre in a sheared two-dimensional foam: Numerical simulations

Langlois

Hutzler

2017

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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Recently there has been a renewed interest in using foamy suspensions of wood fibres as a carrier fluid in papermaking but there is a lack of fundamental understanding of the dynamics of such a three-phase system. In this article we propose a numerical model for the dynamics of an individual flexible fibre within a flowing foam, based on discrete-element methods. As is observed in a Newtonian shear flow, we observe that the fibre systematically experiences a tumbling instability: the disordered motion of bubbles cannot prevent the pseudo-periodical flip of the fibre. Our simulations show that the tumbling time decreases almost as the inverse of the strain rate. It also decays when the fibre length is increased, though for long enough fibres it reaches a constant value. Similarly the tumbling time is also surprisingly independent of the stiffness of the fibre. Because of their tumbling motion, long and flexible fibres spend most of the time in a coiled geometry. This would imply that using foam as a carrier fluid is not enough to keep fibres aligned with the flow. However, further refinements of the model will need to be considered to arrive at firm conclusions regarding alignment. Dear Editor,We would like to thank the referee for his careful reading and constructive remarks. We tried to follow his recommendations, and to answer his comments and concerns regarding the article. The modifications we brought to the paper are listed below:Reviewer #1 * General questions that seem not to be addressed are: Is there shear-banding or localisation? Does it matter where between the side walls the fibre is placed? (I guess it shouldn't, but I presume that this was checked.)Since no additional wall friction is added (see our previous study of the bubble model in Langlois et al. [2008]), no shear-banding is observed. The average velocity profile is mostly undisturbed by the presence of a unique fibre, and remains linear.The initial y-position of the fibre is of no influence, except in the 'pathological' case where it comes in contact with one of the walls and remains there.* lines 10-20 are not very clear on how the presence of the fibres affects these foam properties; it would be useful to expand this section to give the reader more of a feel for the complexity of this area of research and the way in which a foam interacts with fibres.We have added to the introduction a more thorough description on the effects of fibres on the foam, recently observed experimentally (l.15 to 21).* lines 63 and 96: I find the use of the word "spherical" misleading, since in a 2D experiment bubbles are more discoidal than spherical and they are certainly treated here as discs. Once the description of the bubble model is restricted to 2D, I suggest to use "discs" exclusively.In the simulations the bubbles are indeed treated as disks, though we had initially used the term "spheres" since these disks are meant to mimick a bubble raft made of roughly spherical bubbles seen from above. However we agree that this can lead to some confusion...

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Foams

Höhler¹,

Cohen-Addad²

2016

Fluids, Colloids and Soft Materials: An Introduction to Soft Matter Physics

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Rheological properties of the soft-disk model of two-dimensional foams

Cited by 61 publications

References 33 publications

The role of surfactant type and bubble surface mobility in foam rheology

The role of surfactant type and bubble surface mobility in foam rheology

Dynamics of a flexible fibre in a sheared two-dimensional foam: Numerical simulations

Foams

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