Theoretical and Numerical Study of Bubble Blocking in Wetted Hierarchical Porous Structures

Porous media are widely used for gas–liquid phase separation in micro-gravity, but decreasing pore radius often results in both increased critical pressure for bubble penetration and increased flow resistance through the pores. To address this issue, the present study investigates the bubble dynamics within a hierarchical porous structure to optimize phase separation performance. A theoretical model was developed by analyzing the force balance on an isolated gas bubble to predict critical pressure. The Volume of Fluid (VOF) method was utilized to simulate bubble movement at the pore scale, with critical pressure determined by varying the pressure differential between the inlet and outlet. The effects of bubble radius, pore radius, pore length, and secondary pore location on the critical pressure and critical flow rate were analyzed. Hierarchical pores were found to improve the phase separation performance compared to single stage pores. Specifically, the presence of a secondary pore with pore length and radius of 30 μm increased the critical pressure by 110% and the critical flow rate by 26% compared to a single stage pore with a pore radius of 50 μm.