Nonlinear Variable-Diffusivity Moisture Transport in Zero Gravity Porous Media Space Applications

The mass transport in porous media for space applications is complicated by the absence of the stabilizing gravitational potential. Generally, the spatially-resolved moisture diffusivity in porous media is a function of the local saturation. Formal solutions of very few specific variable-diffusivity parabolic flows are known. We are using the finite difference numerical methods to solve the nonlinear wetting and de-wetting diffusion dynamics in microgravity conditions. Two different functional relationships between the saturation and the moisture-diffusivity were considered. The half-saturation action-radius and the zone-of-influence of the porous suction tubes on the cold-plate porous material are especially adversely affected by the exponentially changing, saturation-dependent, diffusivity. Clogging and biofouling dramatically decrease dynamic response and performance of the porous media flow.