Effect of granular packing geometry on evaporation

Understanding evaporation or drying in granular media still remains complex despite recent advancements. Evaporation depends on liquid transport across a connected film network from the bulk to the surface. In this study, we investigate the stability of film networks as a function of granular packing. Using a controlled experimental approach, we vary the granular packing geometry and show the changes in the height of the liquid film network during evaporation as packing shifts from a loose-packed to a close-packed arrangement. This height can be calculated from an equilibrium between hydrostatic pressure and the pressure difference between two points in the vertical film network. We use a simulation approach to calculate the pressure in both the percolating front and evaporating front within the two-phase zone of air/water mixture. Results show good agreement between the model and the experiment.