SCIENCE - Explanation as to when a liquid on a rough surface will form a thin film and when it will form droplets

(Phys.org)-The phenomenon of liquids coating rough surfaces in the form of films or droplets is commonplace. The morning dew converts grass and leaves into scenes of magical beauty, while a thin film of rainwater on the road can pose a danger to every driver - especially if it freezes. But how can we tell in what conditions a liquid will form a continuous film or just isolated drops? Existing theories generally describe ideally smooth surfaces, which are not so relevant in the real world. Now, for the first time, scientists at the Max Planck Institute for Dynamics and Self-Organisation in Göttingen have developed a general theory that provides an answer to the question of film or droplets for rough surfaces. It is based on amazingly simple mathematical expressions - and could make it possible to predict, for instance, whether (and when) short circuits are likely to occur in transformer substations.

http://phys.org/news/2013-01-explanation-liquid-rough-surface-thin.htm