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SUMMARY:A large-deviation approach to passive scalar advection\, diffusion
  and reaction - Vanneste\, J (University of Edinburgh)
DTSTART:20131030T155500Z
DTEND:20131030T163000Z
UID:TALK48583@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Co-authors: Peter H. Haynes (University of Cambridge)\, Alexan
 dra Tzella (University of Birmingham)\n\nThe dispersion of a passive scala
 r in a fluid through the combined action of advection and molecular diffus
 ion can often be described as a diffusive process\, with an effective diff
 usivity that is enhanced compared to the molecular value. This description
  fails to capture the tails of the scalar concentration in initial-value p
 roblems\, however. This talk addresses this issue and shows how the theory
  of large deviation can be applied to capture the concentration tails by s
 olving a family of eigenvalue problems. Two types of flows are considered:
  shear flows and cellular flows. In both cases\, large deviation is shown 
 to generalise classical results (Taylor dispersion for shear flows\, homog
 enisation results for cellular flows). Explicit asymptotic results are obt
 ained in the limit of large Pclet number corresponding to small molecular 
 diffusivity. The implications of the results for the problem of front prop
 agation in reacting flows are also discussed.\n
LOCATION:Seminar Room 1\, Newton Institute
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