Vers la simulation numérique de mousses instables avec surfactants

Les mousses ou matériaux moussés sont utilisés en raison de leur légèreté, de leur porosité, et de leur pouvoir d'isolation thermique et phonique. Cependant, les mousses solides, qui sont fabriquées à partir des mousses liquides, s'effondrent aux hautes porosités. Notre objectif est de comprendre comment une mousse se casse afin d'éviter cet effondrement, en étudiant les mousses liquides. Pour cela, nous développons un modèle numérique pour la simulation directe de mousses qui sont soumises à un cisaillement. Le point-clé est une description explicite des surfactants dans cet écoulement diphasique. Dans ce travail, nous proposons une extension de la méthode de simulation numérique ``Level set'' déjà établie pour des écoulements diphasiques, en prenant en compte la présence de surfactants

Electrostatic forces on charged surfaces of bilayer lipid membranes

Simulating protein-membrane interactions is an important and dynamic area of research. A proper definition of electrostatic forces on membrane surfaces is necessary for developing electromechanical models of protein-membrane interactions. Here we modeled the bilayer membrane as a continuum with general continuous distributions of lipids charges on membrane surfaces. A new electrostatic potential energy functional was then defined for this solvated protein-membrane system. We investigated the geometrical transformation properties of the membrane surfaces under a smooth velocity field. These properties allows us to apply the Hadamard-Zolesio structure theorem, and the electrostatic forces on membrane surfaces can be computed as the shape derivative of the electrostatic energy functional

Computational study of the role of surfactants in sheared foams for foam stability

The dynamics of sheared wet foams is investigated computationally in this study. For this purpose, an established 3D (parallel) implementation of a level-set method for incompressible two-phase flow has been extended to account for the presence of surfactants that are soluble in the liquid, and the associated modified stress conditions at interfaces. In particular, we account for surface rheological behavior (such as surface viscosity) beyond minimal surfactant models, to describe realistic systems. The results of 2D and 3D tests will be demonstrated to compare favourably with the literature. We shall report on the role of surfactants and their properties on T1 events, wherein adjacent bubbles are sheared past each other, with implications for foam instability