Dresden 2014 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 18: Granular Matter / Contact Dynamics
DY 18.5: Talk
Wednesday, April 2, 2014, 10:30–10:45, ZEU 118
Drying in microfluidic cells as a model granular material — •Paolo Fantinel1,2, Oshri Borgman3, Ran Holtzman3, and Lucas Goehring1,2 — 1Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany — 2Georg-August Universität, Göttingen, Germany — 3Dept. of Soil and Water Sciences, Hebrew University, Rehovot, Israel
We study the drying of porous granular materials on a microscopic scale as to understand macroscopic mechanisms. We aim to develop a 2D pore-scale model through experiments. The long-term goal is to extend such class of models to 3D systems. Ours are microfluidic cells made of an array of pillars,representing the soil grains. The cells are open at one end to allow evaporation. The height is modifiable, as to vary pore elasticity, and we introduce different degrees of heterogeneity by randomly changing particle sizes and positions, as would happen in nature.
We fill the cells with a volatile fluid and watch them dry. At first evaporation happens mainly at the surface, then isolated clusters of fluid form. Through image analysis we find the pressure inside the pores by measuring the curvature of the air-water interfaces. We find a fractal dimension for the liquid-vapor interface of 1.4,close to what expected for percolation. We can also measure the variation in cluster volume, establishing the relative importance of flow through connected pores, thin-film flow and vapor diffusion.
Our experiments are being used together with simulations to establish a micro-scale model of drying in porous media.