Numerical investigation of microscale dynamic contact angles of the CO2-water-silica system using coarse-grained molecular approach

The dynamic contact angle of a gas-liquid-solid system depends on the contact line velocity and ignoring this effect could lead to inaccurate estimations of the capillary pressures in microporous media. While most existing coarse-grained molecular dynamics (CGMD) models use one particle to represent a few molecules, we present a novel CGMD framework to model microscale CO2/water flows in silica with each particle representing hundreds of thousands of molecules. The framework can reproduce the densities and viscosities of water and CO2, water-CO(2)interfacial tension, and static contact angle over a wide range of pressures. The validated framework is applied to study the velocity-dependency of contact angle of the microscale CO2-water-silica system. The results indicate that the assumption in the molecular kinetic theory that liquid-solid interaction is similar to the reversible work of adhesion between liquid and solid may not hold for CO2-water-silica systems.