Thermocapillary Forced-drained Foam: Effect of Surface Rheology

Abstract eng:
In this paper, we show that a thermocapillary stress induces a surface flow which can be sufficient to counteract the bulk gravity drainage, i.e. it is possible to stop, or even reverse, the drainage of a liquid foam. We report experiments using either a soluble (SDS) or poorly soluble (DOH) surfactant in a model system, a 2D microfoam, in which the full geometry of the liquid phase is known, leading a priori to accessible modeling. In the former case, surface rheology can be disregarded and a model considering mass conservation allows recovering the experimental results. In the later case, the boundary condition includes Gibbs elasticity (non homogeneous surface concentrtaton of surfactant) and both shear and dilational surface viscosities. In this case, investigating surfactant transport mechanisms could not allow extracting a dominant contribution leading to the conclusion that all surface rheology properties have to be considered.

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