Let’s drop off a mixture of water and alcohol on the surface of an oil bath. If the alcohol content is high enough, the drop spreads and spontaneously blows out in a myriad of droplets. The size of ejected droplets strongly depends on the initial alcohol concentration. As in the “tears of wine” effect, faster evaporation of alcohol induces surface tension gradients (Marangoni effect) that themselves generate flows. The complex coupling between interfacial hydrodynamics, wetting and evaporation can be understood through analytical scaling laws. This phenomenon will be illustrated by an irl demonstration.

Sphere in a tube

What is the necessary force to slide an object in a narrow elastic tube ? Tube constriction causes a normal stress. In the case of a solid friction, Coulomb law allows to straightforwardly deduce the traction force. How does the force evolve in presence of lubricant ? It will be shown how this elasticity and lubrication coupled problem shows analogies with dynamical wetting situations. The coupling particularly results in a nonlinear dependence of the force on the traction speed.

Contact : catherine.quilliet@univ-grenoble-alpes.fr