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Evaporation versus Spreading

  • Supervisor: Prof. dr. Daniel Bonn, dr. Noushine Shahidzadeh
  • Research Team: Etienne Jambon-Puilliet
  • Goal: To understand the evaporation dynamics of wetting liquids.
  • Info: E.Jambon-Puilliet

The evaporation of liquid droplets is a natural phenomenon that occurs everyday. After the dew, during the rain or when sea waves break, evaporation transfers heat and mass to the surrounding atmosphere which must be accounted in climatic models. Droplet evaporation also occurs in industrial processes such as spray drying or ink jet printing as well as when you taste your favorite champagne. It is thus crucial to understand the dynamic of droplet evaporation and as a result it has been studied for more than a century since Maxwell's early work. Here, we look at the evaporation of droplets of completely wetting liquids deposited on a perfectly smooth surface. When depositing a drop, since the liquid is perfectly wetting it starts to spread on the surface to minimize the surface energy. However, since the droplet evaporates at the same time, it starts to recede shortly afterwards, with a constant non zero contact angle. This seemingly simple problem actually involves two mathematical singularities at the contact line that must be regularized. The viscous dissipation near the moving contact line as well as the local evaporation rate diverges with standard hydrodynamics and thermal models. To understand our experiments, a careful examination of the microscopic region near the moving edge of the drop must be matched with its global macroscopic behavior.