Nonlinear Variable-Diffusivity Moisture Transport in Zero Gravity Porous Media Space Applications 2009-01-2584
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.