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SUMMARY:Local and nonlocal energy transfers in a family of geophysically r
 elevant 2D turbulence models - Bel Helen Burgess (University of Toronto)
DTSTART:20120621T120000Z
DTEND:20120621T130000Z
UID:TALK38598@talks.cam.ac.uk
CONTACT:Dr Ed Brambley
DESCRIPTION:We study the spectral nonlocality of generalized energy transf
 ers in alpha-turbulence models. These include planetary geostrophic dynami
 cs (alpha = -2)\, surface quasi-geostrophic dynamics (alpha = 1)\, familia
 r 2D Navier-Stokes flow (alpha = 2)\, and rotating shallow flow (RSF\, alp
 ha = 3)\, the isotropic limit of a mantle convection model. We first use F
 jortoft-style arguments to study the dependence of wavevector triad geomet
 ry on alpha. Such arguments provide no information on triad activity. We t
 hen derive for alpha-turbulence the eddy damped quasinormal Markovian (EDQ
 NM) closure. Combined with a similarity assumption\, this allows us to cal
 culate\, in first approximation\, the contributions of particular triad sh
 apes to the generalized energy flux. As alpha increases\, contributions fr
 om long\, thin\, nonlocal triads increasingly dominate the flux\; starting
  at alpha = 4\, the flux diverges\, signaling complete breakdown of transf
 er locality. In comparison\, the EDQNM generalized enstrophy flux diverges
  at alpha = 2.\n\nInterestingly\, for alpha > 2.5\, the net generalized en
 ergy flux associated with the self-similar inertial range solution is towa
 rd small scales (i.e. downscale)\, rather than large scales. This downscal
 e flux reflects the relationship between the similarity spectrum and the t
 wo-temperature equipartition spectrum calculated for a spectrally truncate
 d fluid. 
LOCATION:MR5 (NB not the usual MR2)\, Centre for Mathematical Sciences\, W
 ilberforce Road\, Cambridge
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