The geometric characteristics and physical properties of the liquid-vapor interface in porous media such as soil or other geomaterials reflect the occurrence state of water in porous media and affect the hydraulic and mechanical properties of porous media. For submicron or nanoscale pores, the solid matrix of porous media has a strong adsorption effect on the liquid and exerts a non-negligible influence on the geometric characteristics and physical properties of the liquid-vapor interface.

Professor Dong Yi, a research fellow at the Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, has long been devoted to research on multiphase geomaterial mechanics and engineering, including theories related to heat and mass transfer and phase change involved in multiphase flow in porous media. Addressing the question of how adsorption affects the properties of the liquid-vapor interface in pores, and based on thermodynamic principles, he derived through the variational method specific generalized Young-Laplace equations describing the liquid-vapor interface in two idealized pores; by introducing van der Waals forces, electrostatic forces, and structural forces in the disjoining pressure to describe adsorption, he analyzed in detail the influence of adsorption on geometric characteristics such as the morphology and curvature of the liquid-vapor interface and on the physical characteristic of the interfacial air-water pressure difference, and explored from the perspectives of water content and pore size how scale effects enhance the influence of adsorption on the liquid-vapor interface and how the wettability of solid surfaces varies with scale; through the interfacial profile parameters of the liquid-vapor interface, he characterized the relationship curves of matric potential and interparticle forces versus pore water content, and described and analyzed the influence of adsorption on the hydraulic and mechanical properties of pores. These research results provide a theoretical basis for studying physicochemical processes related to liquid-vapor interface properties, such as liquid phase change, crystal growth, and bubble nucleation during liquid cavitation, and also provide a basic framework for studying how adsorption affects the water retention and mechanical properties of natural porous media and other geotechnical materials.

The above research was funded by the National Natural Science Foundation of China under grants NSFC-41702338 and NSFC-51779254, and the results were published as the paper "How solid–liquid adsorption affects the liquid–vapor interface in pores" in the SSSAJ journal Vadose Zone Journal.

Paper link: https://doi.org/10.1002/vzj2.20214

Fig. 1 Schematic diagram of the physical model of the liquid-vapor interface between two spherical particles considering adsorption

Fig. 2 Liquid-vapor interface profiles between spherical particles at different half-filling angles, and distributions of interfacial curvature and interfacial pressure difference