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

Abstract

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–CO2 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.