Decoupling of the effects of inertial and transverse capillary forces on bubble breakthrough in porous structures

Porous media are extensively employed in gas–liquid separation processes due to their remarkable capillary effects arising from the pores at the micro/nanoscale. However, the coupling between inertial and transverse capillary forces and their respective influences on bubble breakthrough remain insufficiently understood. We designed porous structures with imposed transverse capillary pressures by adding transverse pores to rectangular channels and used an equivalent transverse pressure method to experimentally quantify how transverse capillary forces influence bubble dynamics, the bubble point pressure, and the critical flow rate. The gas–liquid flow patterns were characterized using high-speed imaging and microscopic particle image velocimetry. Compared with pores without imposed transverse pressure, increasing the transverse capillary number to 0.71 for isopropanol and 0.97 for HFE7500, corresponding to an imposed transverse pressure of 600 Pa, leads to notable increases in the normalized bubble point pressure and critical flow rate for a main pore size of 100 μm, reaching 18.7% and 7.5% for isopropanol and 27.5% and 13.4% for HFE7500, respectively. This enhancement is governed by a synergistic competition mechanism. Transverse pore structures increase the bubble point pressure via contact-line pinning, whereas sufficiently large transverse pressure partially offsets the pinning effect and further strengthens interfacial wetting. These results elucidate the interplay between inertia and transverse capillarity in porous media and provide practical guidance for optimizing the design of capillary-wetted porous structures for efficient gas–liquid separation.