Journal of Fluid Mechanics


Evaporating droplets

a1 Laboratoire des Matériaux et Structures du Génie Civil, 2 allée Kepler 77420 Champs sur Marne, France
a2 Laboratoire de Physique Statistique de l'ENS, 24 rue Lhomond 75231 Paris Cedex 05, France
a3 Van der Waals-Zeeman institute, University of Amsterdam, Valckenierstraat 65 1018 XE Amsterdam, the Netherlands

Article author query
shahidzadeh-bonn n   [Google Scholar] 
rafai s   [Google Scholar] 
azouni a   [Google Scholar] 
bonn d   [Google Scholar] 


The evaporation of droplets on a substrate that is wetting to the liquid is studied. The radius $R(t)$ of the droplet is followed in time until it reaches zero. If the evaporation is purely diffusive, $R \propto \sqrt{t_0\,{-}\,t}$ is expected, where $t_0$ is the time at which the droplet vanishes; this is found for organic liquids, but water has a different exponent. We show here that the difference is likely to be due to the fact that water vapour is lighter than air, and the vapour of other liquids more dense. If we carefully confine the water so that a diffusive boundary layer may develop, we retrieve $R(t) \propto \sqrt{t_0\,{-}\,t}$. On the other hand, if we force convection for an organic liquid, we retrieve the anomalous exponent for water.

(Published Online February 8 2006)
(Received August 29 2005)
(Revised November 15 2005)