This project involves an experimental study of the moisture transport process that occurs during the drying of granular porous media. In principle, the mechanisms are quite simple--diffusion of water vapor in the gas phase owing to gradients in the partial pressure and convection in the liquid phase owing to capillary forces. Recent visual studies have clearly indicated that the influence of local heterogeneities is dominated by two parameters: the Bond number (ratio of surface tension effects to gravitiational effects) and the variance of the particle size distribution. To explore a wide range of Bond numbers, the investigator will use packed beds of glass spheres ranging from 100 to 1000 microns. The influence of the variance of the particle size distribution will be explored using mixtures of spherical particles and mixtures of crushed glass particles.
