Every year, during the Fluid Dynamics conference organised by the American Physical Society, there is a competition to find the best film-demonstration of phenomena related to fluid mechanics. Alexis Duchesne (post-doc), Charles Dubois (doctoral student ARC) and Hervé Caps (professor) at GRASP (Group for Research and Applications in Statistical Physics) of the University of Liege, have won first prize in a competition involving more than 100 videos.
It was observed that if the temperature of the wire is less than the boiling temperature of the liquid (silicon oil in this case), nothing happens. Beyond this temperature, bubbles appear. Two surprising phenomena then occur: (i) despite the fact that the bubbles are lighter than the liquid, they do not rise to the surface but remain “stuck” to the wire; (ii) they move…and do so very quickly (almost 10cm/second).
When two bubbles meet, they can rebound off each other or coalesce. When several bubbles have merged, the resulting bubble can become large enough to escape the “attraction” of the wire and break away. By increasing the heat of the wire, clusters of bubbles form. These clusters are fixed and isolated bubbles rebound between them. By increasing the temperature of the wire even more, it is possible to create clusters of bubbles that are the same size as the wire while creating a surprisingly calm environment in this boiling liquid.