Critère d'instabilité du front de retrait lors du séchage lent d'une suspension d'argile dans un dièdre

Abstract

Drying a clay-water suspension within a dihedral leads to the formation of dry clay veils which result from the instability of the withdrawing front. Considering that the suspension dries but no significant gradient of solid fraction develops, the fluid withdrawal can be considered as the flow of a yield stress fluid subjected to the Saffman-Taylor instability. A simple theoretical approach shows that the flow is unstable when the yield stress of the fluid is larger than a critical value proportional to the local distance between the solid surfaces and proportional to the surface tension. The position of the first veils predicted by this theory as a function of the initial solid fraction of the suspension is in agreement with the experiments.