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SUMMARY:Thermally and mechanically driven quantum turbulence in helium II 
 - Sherwin\, L (Newcastle University)
DTSTART:20121203T115000Z
DTEND:20121203T121000Z
UID:TALK41779@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:In most experiments with superfluid helium\, turbulence is gen
 erated thermally (by applying a heat flux\, as in thermal counterflow) or 
 mechanically (by stirring the liquid). By modeling the superfluid vortex l
 ines as reconnecting space curves with fixed circulation\, and the driving
  normal fluid as a uniform flow (for thermal counterflow) and a synthetic 
 turbulent flow (for mechanically driven turbulence)\, we determine the dif
 ference between thermally and mechanically driven quantum turbulence. We f
 ind that in mechanically driven turbulence\, the energy is concentrated at
  the large scales\, the spectrum obeys Kolmogorov scaling\, vortex lines h
 ave large curvature\, and the presence of coherent vortex structures induc
 es vortex reconnections at small angles. On the contrary\, in thermally dr
 iven turbulence\, the energy is concentrated at the mesoscales\, the curva
 ture is smaller\, the vorticity field is featureless\, and reconnections o
 ccur at larger angles. Our results suggest a method t o experimentally det
 ect the presence of superfluid vortex bundles.\n
LOCATION:Seminar Room 1\, Newton Institute
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