Multiple imbibition of a porous medium in microgravity: experiments and simulation

The paper considers multiple successive imbibitions of a porous medium due to capillary forces in microgravity. Such studies are of great importance both for space and Earth technologies. For example, on space stations liquid flows due to capillary effects can be observed in heat pipes, purification systems, and hydroponic plant growing systems growing plants. Under the Earth's gravity, capillary phenomena significantly affect seepage flows (e.g., in hydrocarbon production) when several fluids flow simultaneously through a porous medium.
Observing capillary effects under normal gravity is difficult because gravity dominates over capillary forces, masking some key aspects. This paper discusses experimental studies of liquid flows through a highly permeable porous medium during parabolic flights. The results show that with each subsequent parabola arc, the liquid rises higher, i.e. there is more intensive imbibition in the already wetted medium. To simulate such processes, special models are required to consider hysteresis. The paper covers such models and presents the simulation results. The experimental data and simulation of seepage fluid flows are compared. Unknown empirical constants can be estimated experimentally.