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SUMMARY:Statistics and growth rates of high-amplitude vorticity events in 
 turbulence - Schumacher\, J (TU Ilmenau)
DTSTART:20080930T130000Z
DTEND:20080930T133000Z
UID:TALK13848@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Fluid turbulence is often characterized as a tangle of many in
 termittent vortices embedded in regions of straining motion. Although ther
 e have been many experimental and numerical studies on the evolution of is
 olated intense vortices\, pairs of them or on the kinematics of ensembles 
 of randomly distributed vortices\, not much is known about their dynamic e
 volution in a fully turbulent flow. We present a high-resolution numerical
  simulation that monitors the formation and time evolution of high-amplitu
 de vorticity regions. In order to identify and follow these events\, we tr
 ack the turbulence fields in local Cartesian frames of reference which mov
 e with Lagrangian tracers through the fluid. The local enstrophy -a measur
 e of vorticity- shows temporal growth compatible on average with a classic
 al prediction by Howarth and von Karman (1938). It remains well below a re
 cently predicted rigorous upper bound for the enstrophy growth (Lu and Doe
 ring\, 2008). However locally\, enstrophy growth rates are detected that g
 o beyond the mean trend and approach the predicted global bound.\nRelated 
 Links\n\n    * http://www.tu-ilmenau.de/tsm - Homepage of Theoretical Flui
 d Mechanics Group\n
LOCATION:Seminar Room 1\, Newton Institute
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