Effects of inertia on the hydrodynamics near moving contact lines

We investigate the effects of inertia on the hydrodynamics in the microscop ic vicinity of moving contact lines. These hydrodynamics control the macros copic shape and spreading of fluid bodies across solid surfaces. We perform experiments at low capillary number (Ca < 0.1) and negligible (10(-4)) to moderate (Re similar to 1) Reynolds number. On a microscopic scale, inertia decreases the dynamic curvature of the free surface near the contact line compared to the case with Re=0 at the same Ca. On a macroscopic scale, iner tia lowers the apparent contact angle of the static-like macroscopic interf ace compared to the situations with the same Ca but negligible Re. (C) 1999 American Institute of Physics. [S1070-6631(99)02611-2].