Surface tension and wetting effects with smoothed particle hydrodynamics

For flows at the micro and nano scales the surface to volume fraction is increased and therefore the behavior of fluids in contact with solid structures is primarily dominated by surface tension effects. Modeling of surface tension effects at nano and micro scales using smoothed particle hydrodynamics requires an efficient description not only of the interface between liquid and gas, but also of the triple line defined by the three phase contact between the solid, liquid and gas. In this study, we propose an efficient and reliable implementation, which takes the liquid-gas surface tension and the equilibrium contact angle as input parameters and prescribes the normal direction of the liquid-gas interface at the triple line based on the desired equilibrium contact angle. This results in a robust algorithm capable of capturing the physics of equilibrium wetting and treating a large variety of cases including different wetting angles, pinning effects and wetting of structu red surfaces.