Gas migration in a soft granular material



In collaboration with Prof. Chris MacMinn (Oxford), we studied two-phase flows inside soft porous media by injecting air into a vertical, quasi-2D packing of soft hydrogel beads saturated with water. The use of highly deformable and nearly transparent hydrogel particles enables clear visualization and high-resolution measurements of both flow and solid deformation in the novel laboratory experiments. We systematically increased the confining pre-stress in the packing by compressing it with a fluid-permeable piston, leading to a gradual transition in migration mechanism from fluidization to pathway opening to pore invasion. By connecting these mechanisms quantitatively with macroscopic invasion, trapping, and venting, we showed that the mixed-mode transitional regime enables a sharp increase in the amount of gas trapped within the packing. Inspired by this observation, we conducted systematic experiments and discrete particle simulations to suspend rising bubbles on demand, by actively modulating soft granular materials.

S. Lee1, J. Lee, R. Le Mestre, F. Xu*, and C. MacMinn1, “Migration, trapping, and venting of gas in a soft granular material,” Physical Review Fluids (2020) 5, 084307
1co-corresponding authors