Impact of Pressure Waves on Water Imbibition and Flow in Unsaturated Porous Media

The wetting front dynamics during water imbibition in dry porous media affect the ultimate water distribution pattern. In this study, we investigate the impact of pressure pulses that emit waves in the water phase on the water distribution and imbibition patterns in porous media. We present experimental results of water spatial distribution in sand columns following infiltration under abrupt pressured-water pulses and compare them with those of continuous inflow. Applying pressure waves during infiltration increases pressure gradients behind the wetting front, which can overcome capillary and gravitational forces, leading to uniform imbibition. To simulate the process, we developed a pore-network model incorporating an analytical solution of pressure wave attenuation to predict the imbibition pattern. Our results demonstrate that the amplitude of the pressure wave is associated with a sharp wetting front, resulting in higher water content compared to Darcy-type continuous flow. The findings suggest that pressure waves have the potential to achieve high water content in unsaturated media and provide insights into the spatial extent of their impact on water distribution.