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SUMMARY:Novel Ways of Describing Complex Fluid Flow:  Curvature\, Topology
 \, and Stretching Fields - Jerry Gollub\, Haverford/Upenn and DAMTP
DTSTART:20081017T150000Z
DTEND:20081017T160000Z
UID:TALK14477@talks.cam.ac.uk
CONTACT:Raymond E. Goldstein
DESCRIPTION:Fluid flows that are spatiotemporally chaotic but not turbulen
 t are hard to characterize and understand. This lecture will present new w
 ays of describing such flows\, in part to characterize their ability to pr
 oduce mixing and transport.  (a) Complex flows can be characterized by th
 eir special topological points.  These special points can be detected and
  followed in real time by measuring the curvature of particle trajectories
 \, and to use this information to study the transition to spatiotemporal c
 haos.  The special points are found to be pinned to the forcing when the 
 driving is weak\, but wander over the flow and interact in pairs when the 
 flow is stronger.  Their behavior reveals a two-stage transition to spati
 otemporal chaos: a gradual loss of spatial and temporal order followed by 
 an abrupt onset of topological changes.  Another powerful way to describe
  complex flows is to determine their "stretching fields" (spatially resolv
 ed finite time Lyapunov exponent fields)\, which are very useful in descri
 bing mixing and reactions in fluid flows.
LOCATION:MR2\, Centre for Mathematical Sciences\, Wilberforce Road\, Cambr
 idge
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