Evaporation in porous media : pore network simulations and continuum modelling

Drying of porous media is at the heart of many environmental and industrial processes. In this thesis, we are interested in capillary porous media, a category typically corresponding to pore sizes in the micron range. Modeling of drying is traditionally carried out within the classical framework of the continuum approach to porous media. Although widely used, the corresponding models cannot be considered as fully predictive so that the theory of drying porous media in the continuous framework can be still considered as incomplete. A well-identified difficulty of the continuum approach is the coupling with external transfers. In this thesis, this point is studied from comparisons with simulations on a pore network model by focusing on the regime dominated by capillary effects and the first period of drying during which the surface of the porous medium is partially wetted. This coupling is studied based on the concepts of interfacial resistance and effective surface. The interfacial resistance is characterized in detail from the pore network simulations. In a second part, we focus on another major characteristic of drying: the fact that the liquid phase breaks up into numerous clusters. This leads to the development of a continuum three-equation model in which the liquid phase is decomposed into a percolating liquid phase and a non-percolating liquid phase. Very good agreement between this model and the pore network simulations is obtained. Finally, this three-equation model is extended to the case where a solute is present in the liquid phase. This leads to a continuum model with five equations. Here again, a very good agreement is obtained between the continuum modeling and simulations on a pore network