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SUMMARY:Surfactant transport onto a foam lamella taking into account surfa
 ce viscosity - Vitasari\, D (University of Manchester)
DTSTART:20140225T163500Z
DTEND:20140225T170000Z
UID:TALK51075@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Co-authors: Paul Grassia (The University of Manchester)\, Pete
 r Martin (The University of Manchester) \n\nThe transport of surfactant on
 to a foam lamella in a foam fractionation column with reflux has been simu
 lated mathematically. Insoluble surfactant is assumed since such surfactan
 ts potentially derive more benefit from a reflux system. The transport of 
 surfactant on the surface of a lamella is governed by the film drainage to
 wards the Plateau border\, the Marangoni effect in the direction towards t
 he centre of the film and possibly also the surface viscous effect that ba
 lances the resultant of the other forces. The desirable condition is when 
 the Marangoni effect dominates the film drainage\, where surfactant accumu
 lates on the surface of the lamella. The surface viscous effect takes plac
 e when there is movement on the surface and it slows down the velocity on 
 the surface. In this study\, a case without film drainage is examined as a
  benchmark for more complicated systems. A mathematical model of the surfa
 ce velocity has been developed and results in a differential equation for 
 s urface velocity which is solved using the finite difference method. The 
 calculated surface velocity is used to compute the evolution of surfactant
  surface concentration using a material point method. The model is verifie
 d using analytical solutions for the special case where the surface viscou
 s effect is very small. The numerical model is verified using the analytic
 al solution in the special case where the gradient of the logarithm of sur
 face concentration is linear in space. The Green's function solution of th
 e differential equation is also used to verify the numerical model. The re
 sult of the simulation in the presence of surface viscosity is compared wi
 th the simulation result in the absence of surface viscosity. It was found
  that the surface velocity slows down markedly near the Plateau border due
  to the effect of surface viscous stress. At any given time\, the surfacta
 nt surface concentration in the presence of surface viscosity is lower tha
 n that in the absence of surface viscosity.\n
LOCATION:Seminar Room 1\, Newton Institute
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