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SUMMARY:Wetting and elasticity: 2 experimental illustrations - Jose Bico (
 ESPCI Paris)
DTSTART:20180223T160000Z
DTEND:20180223T170000Z
UID:TALK99283@talks.cam.ac.uk
CONTACT:Doris Allen
DESCRIPTION:1. Marangoni bursting\nDepositing a droplet of pure water on a
  bath of sunflower oil is generally a frustrating experience as it leads t
 o a steady liquid lens. However\, if water is replaced by a mixture of alc
 ohol and water\, a spectacular phenomenon is observed: the droplet spreads
  and then spontaneously fragments into a myriad of minute droplets. The si
 ze of the expelled droplets strongly depends on the initial concentration 
 of alcohol. As in the case of the famous "tears” that wine lovers apprec
 iate\, Marangoni flows induced by the evaporation of alcohol play a key ro
 le in the overall dynamics. The intricate coupling of hydrodynamics\, wett
 ing\, and evaporation can be captured by analytical scaling laws\, althoug
 h the detail of the instability remains to be understood.\n\n2. Moving a w
 ide sphere in a narrow elastic tube\nWhat is the force required to move an
  object inside a narrow elastic pipe? The constriction by the tube induces
  a normal force on the sphere. In the case of solid friction\, the pulling
  force may be simply deduced from Coulomb’s law. How is such force modif
 ied by the addition of a lubricant liquid? This coupled problem between el
 asticity and viscous flow shares some analogies with the seminal works of 
 Bretherton on liquid coating. In particular\, such coupling results in a n
 on-linear dependence of the force on the traction speed.
LOCATION:MR2\, Centre for Mathematical Sciences\, Wilberforce Road\, Cambr
 idge
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