Fluid epitaxialization effect on velocity dependence of dynamic contact angle in molecular scale

摘要

Molecular dynamics simulations were used to investigate the effect of epitaxial ordering of the fluidmolecules on the microscopic dynamic contact angle. The simulations were performed in aCouette-flow-like geometry where two immiscible fluids were confined between two parallel wallsmoving in opposite directions. The extent of ordering was varied by changing the number densityof the wall particles. As the ordering becomes more evident, the change in the dynamic contactangle tends to be more sensitive to the increase in the relative velocity of the contact line to the wall.Stress components around the contact line is evaluated in order to examine the stress balance amongthe hydrodynamic stresses (viscous stress and pressure), the deviation of Young’s stress from thestatic equilibrium condition, and the fluid-wall shear stress induced by the relative motion betweenthem. It is shown that the magnitude of the shear stress on the fluid-wall surface is the primarycontribution to the sensitivity of the dynamic contact angle and that the sensitivity is intensified bythe fluid ordering near the wall surface.