Dynamics of immiscible-fluid displacement in a capillary tube

Through first-principles hydrodynamic calculations, the macroscopic behavior of the displacement of immiscible fluids in a capillary tube is linked to the microscopic parameters governing the dynamics of the moving contact line. Comparison with experimental data reveals that the contact line is dragged by a frictional force varying as $U^x$, where U is the mean flow velocity and x≃(1/2. Consideration of capillary-wave excitation at the fluid-fluid interface as the source mechanism of this frictional force yields predictions in excellent agreement with experimental data.