WAITING-TIME BEHAVIOR FOR LARGE-ANGLE WEDGES OF VISCOUS-LIQUIDS

We experimentally study plane viscous gravity flows starting from tria ngular prism-shaped configurations with large angles alpha between the free surface and the substrate (15 degrees less than or equal to alph a less than or equal to 70 degrees). We measure the time t(w) (waiting time) that the contact line (front) waits before moving and determine the evolution of both the thickness and slope distributions near the front for t less than or equal to t(w). The waiting time is approximat ed by the evolution time of the global flow throughout the angular ran ge. An unexpected finite value of t(w) for alpha > 45 degrees is proba bly due to a surface tension effect.