Air Entrainment Through Free-Surface Cusps homepage paper(ps)
Saturday, January 13, 2001 - 9:00am - 9:45am
In many industrial processes, such as pouring a liquid or coating a rotating cylinder, air bubbles are entrapped inside the liquid. We propose a novel mechanism for this phenomenon, based on the instability of cusp singularities that generically form on free surfaces. The air being drawn into the narrow channel of a cusp destroys its stationary shape when the walls of the channel come too close. Instead, a sheet emanates from the cusp's tip, through which air is entrained. Our analytical theory of this instability is confirmed by experimental observation and quantitative comparison with numerical simulations of the flow equations.