Kinematics in a slowly drying porous medium: Reconciliation of pore network simulations and continuum modeling

Alireza Attari Moghaddam (1) , Abdolreza Kharaghani (1) , Evangelos Tsotsas (1) , Marc Prat (2)

1 OVGU - Otto-von-Guericke-Universität Magdeburg = Otto-von-Guericke University [Magdeburg]
2 IMFT - Institut de mécanique des fluides de Toulouse

We study the velocity field in the liquid phase during the drying of a porous medium in the capillaritydominated regime with evaporation from the top surface. A simple mass balance in the continuum framework leads to a linear variation of the filtration velocity across the sample. By contrast, the instantaneous slice-averaged velocity field determined from pore network simulations leads to step velocity profiles. The vertical velocity profile is almost constant near the evaporative top surface and zero close to the bottom of the sample. The relative extent of the two regions with constant velocity is dictated by the position of the most unstable meniscus. It is shown that the continuum and pore network results can be reconciled by averaging the velocity field obtained from the pore network simulations over time. This opens up interesting prospects regarding the transport of dissolved species during drying. Also, the study reveals the existence of an edge effect, which is not taken into account in the classical continuum models of drying.

Mots clés: Drying; Porous media

Domaines: Mécanique des fluides [physics.class-ph]

Alireza Attari Moghaddam, Abdolreza Kharaghani, Evangelos Tsotsas, Marc Prat. Kinematics in a slowly drying porous medium: Reconciliation of pore network simulations and continuum modeling. Physics of Fluids, 2017, vol. 29 (n° 2), pp. 1 -13. ⟨10.1063/1.4975985⟩. ⟨hal-01798170⟩