High Reynolds number oscillating contact lines

For the eventual use as regards wave generation and damping, we investigate oscillating contact lines on vertical walls. Stainless steel is used rather than the glass of Ting and Perlin [J. Fluid Mech. 295 (1995) 263] for the vertically sinusoidally oscillating plate over a large range of Reynolds numbers. The non-wetting stainless steel minimizes the static meniscus ignored in our analysis. Other than the change in static contact angle serving as an initial condition, the dynamic features in both cases are similar. In low Reynolds number oscillation, a pinned-edge condition can appropriately describe the contact-line motion. Higher Reynolds number oscillatory contact-line behavior becomes non-linear and very complicated. The resulting periodic, non-sinusoidal oscillation of the contact line exhibits three types of apparent motion: stick (associated with contact angle hysteresis), partial stick where only portions of the oscillation cycle exhibit stick, and total slip. Increasing the Reynolds number reduces hysteresis phenomena, however, it still cannot be ignored. It is seen that the static contact angle is unimportant; it is the dynamic contact angle that is consequential. © 2003 Elsevier B.V. All rights reserved.