Simulation et modélisation multiéchelles de la rhéologie des mousses 2D

We show how macroscopic flow, slow viscoelastic dynamics and rheological memory of 2D liquid foams are related to processes at the film scale and how these are coupled to aging phenomena.The first main topic that we have studied is the coupling between local, mesoscopic and macroscopic length scales. We present a new law relating the stretching of individual films in response to a macroscopic strain. This relationship allows the elasticity of 2D foams to be modelled as function of the microstructure. Moreover, we discuss how macroscopic flow results from bubble rearrangements that can be represented as force dipoles acting within an elastic continuous medium.The second main topic concerns is the coupling between rheology and aging. Using the dipole picture, we establish an analytic expression of the strain due to rearrangements induced by aging. On this basis, we formulate a constitutive rheological model considering intrinsic aging dynamics as well as topological and geometrical constraints.Nous montrons comment l'écoulement, la dynamique viscoélastique lente et la mémoire rhéologique des mousses liquides 2D à l'échelle macroscopique s'expliquent par des processus à l'échelle des films et bulles et comment ils sont couplés au vieillissement.Un premier fil conducteur est le couplage entre les échelles macroscopique, mésoscopique et locale. Nous montrons que l'allongement d'un film individuel sous l'effet d'une déformation macroscopique suit une nouvelle loi qui permet de modéliser l'élasticité des mousses 2D en fonction de la microstructure. Par ailleurs, nous discutons comment un écoulementmacroscopique résulte de réarrangements de bulles agissant comme des dipôles de force au sein d'un milieu continu élastique.Un second fil conducteur est le couplage entre rhéologie et vieillissement. A l'aide de la représentation dipolaire, nous établissons une loi analytique décrivant la déformation induite par les réarrangements dus au vieillissement. Sur cette base, nous formulons un modèle rhéologique constitutif prenant en compte la dynamique intrinsèque due au vieillissement, et les contraintes géométriques et topologiques

Simulation et modélisation multiéchelles de la rhéologie des mousses 2D

We show how macroscopic flow, slow viscoelastic dynamics and rheological memory of 2D liquid foams are related to processes at the film scale and how these are coupled to aging phenomena.The first main topic that we have studied is the coupling between local, mesoscopic and macroscopic length scales. We present a new law relating the stretching of individual films in response to a macroscopic strain. This relationship allows the elasticity of 2D foams to be modelled as function of the microstructure. Moreover, we discuss how macroscopic flow results from bubble rearrangements that can be represented as force dipoles acting within an elastic continuous medium.The second main topic concerns is the coupling between rheology and aging. Using the dipole picture, we establish an analytic expression of the strain due to rearrangements induced by aging. On this basis, we formulate a constitutive rheological model considering intrinsic aging dynamics as well as topological and geometrical constraints.Nous montrons comment l'écoulement, la dynamique viscoélastique lente et la mémoire rhéologique des mousses liquides 2D à l'échelle macroscopique s'expliquent par des processus à l'échelle des films et bulles et comment ils sont couplés au vieillissement.Un premier fil conducteur est le couplage entre les échelles macroscopique, mésoscopique et locale. Nous montrons que l'allongement d'un film individuel sous l'effet d'une déformation macroscopique suit une nouvelle loi qui permet de modéliser l'élasticité des mousses 2D en fonction de la microstructure. Par ailleurs, nous discutons comment un écoulementmacroscopique résulte de réarrangements de bulles agissant comme des dipôles de force au sein d'un milieu continu élastique.Un second fil conducteur est le couplage entre rhéologie et vieillissement. A l'aide de la représentation dipolaire, nous établissons une loi analytique décrivant la déformation induite par les réarrangements dus au vieillissement. Sur cette base, nous formulons un modèle rhéologique constitutif prenant en compte la dynamique intrinsèque due au vieillissement, et les contraintes géométriques et topologiques

Simulation et modélisation multiéchelles de la rhéologie des mousses 2D

Nous montrons comment l écoulement, la dynamique viscoélastique lente et la mémoire rhéologique des mousses liquides 2D à l échelle macroscopique s expliquent par des processus à l échelle des films et bulles et comment ils sont couplés au vieillissement. Un premier fil conducteur est le couplage entre les échelles macroscopique, mésoscopique et locale. Nous montrons que l allongement d un film individuel sous l effet d une déformation macroscopique suit une nouvelle loi qui permet de modéliser l élasticité des mousses 2D en fonction de la microstructure. Par ailleurs, nous discutons comment un écoulement macroscopique résulte de réarrangements de bulles agissant comme des dipôles de force au sein d un milieu continu élastique. Un second fil conducteur est le couplage entre rhéologie et vieillissement. A l aide de la représentation dipolaire, nous établissons une loi analytique décrivant la déformation induite par les réarrangements dus au vieillissement. Sur cette base, nous formulons un modèle rhéologique constitutif prenant en compte la dynamique intrinsèque due au vieillissement, et les contraintes géométriques et topologiquesWe show how macroscopic flow, slow viscoelastic dynamics and rheological memory of 2D liquid foams are related to processes at the film scale and how these are coupled to aging phenomena. The first main topic that we have studied is the coupling between local, mesoscopic and macroscopic length scales. We present a new law relating the stretching of individual films in response to a macroscopic strain. This relationship allows the elasticity of 2D foams to be modelled as function of the microstructure. Moreover, we discuss how macroscopic flow results from bubble rearrangements that can be represented as force dipoles acting within an elastic continuous medium. The second main topic concerns is the coupling between rheology and aging. Using the dipole picture, we establish an analytic expression of the strain due to rearrangements induced by aging. On this basis, we formulate a constitutive rheological model considering intrinsic aging dynamics as well as topological and geometrical constraintsPARIS-EST Marne-la-Vallee-BU (774682101) / SudocSudocFranceF

Daisy-shaped liquid bridges in foam-filled granular packings

International audienceHypothesis: Many applications of liquid foams use them to fill the porosity of various granular media. How is the liquid distributed in such foam-filled systems, in which the geometry of the bubble assembly can be strongly constrained by pore confinement? Experiments: We study how the liquid is distributed in a grain packing filled with liquid foam, as a function of both liquid content and bubble-to-grain size ratio. Moreover, Surface Evolver simulations are carried out at the scale of a single bubble confined into a tetrahedral pore. Findings: We reveal that foam-filled granular assemblies exhibit a robust pendular-like regime, which is reminiscent of the pendular regime in unsaturated media. The main difference is that here the liquid bridges are daisy-shaped, i.e. with a liquid core bounded by bubbly petals. A simple theoretical model is proposed to describe the foam liquid bridges between contacting grains. In the case of large bubbles, the model is compared with the Surface Evolver simulation. The model is also applied to the case of wall liquid bridge, which is compared with the experimental observation. Beyond their geometrical characteristics, the presence of these liquid bridges, which can represent almost 25% of the liquid contained in the porosity, makes it possible to imagine a new approach (binder foam-based) to bind granular assemblies and turn them to solid materials

Liquid relative permeability through foam-filled porous media: Experiments

International audienceFor some applications involving liquid foams, such as soil remediation for example, the liquid relative permeability of the foam-filled porous medium is a crucial parameter as it sets the liquid flow rate at which active substances or nutrients (for bacteria) can be delivered deep into the medium. We are interested in the liquid relative permeability of foam-filled porous media, within the range of low liquid saturations, i.e., ≲ 20 vol % . We fill porous media (packed spherical grains) with different foams made from either alkyl polyglucosides (APG) or saponin, in such a manner that we obtain highly controlled samples in terms of the bubble-to-grain size ratio r and the liquid saturation. The liquid relative permeability of saponin samples exhibits an optimal value as a function of r, while it increases significantly for APG foams. The ratio of their relative permeability of APG/saponin reveals two regimes as a function of r: for r ≲ 0.25, the permeability ratio is equal to the ratio corresponding to the bulk foams, while for larger r values, the permeability ratio is increased by one order of magnitude. The foam microstructure changes a lot as the bubble-to-grain size ratio increases up to 0.5, so that a new liquid network is activated, made of surface channels and liquid bridges, the former connecting the latter even at low liquid saturation. These new liquid elements may greatly benefit foams with mobile interfaces such as APGs. One such issue would deserve a dedicated study to be elucidated