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SUMMARY:Spectral analysis of the transition to turbulence from a dipole in
  stratified fluid - Pierre Augier (DAMTP)
DTSTART:20140221T161200Z
DTEND:20140221T162200Z
UID:TALK51084@talks.cam.ac.uk
CONTACT:Dr C. P.  Caulfield
DESCRIPTION:We investigate through numerical simulations the spectral prop
 erties of the turbulence generated during the nonlinear evolution of a Lam
 b-Chaplygin dipole in a stratified fluid for a high Reynolds number Re = 2
 8000 and a wide range of horizontal Froude number Fh∈[0.0225 0.135] and 
 buoyancy Reynolds number R=ReFh^2∈[14 510]. A spectral analysis shows th
 at this transition is dominated by two kinds of transfers: first\, the she
 ar instability induces a direct non-local transfer toward horizontal wavel
 engths of the order of the buoyancy scale L_b=U/N\, where U is the charact
 eristic horizontal velocity of the dipole and N the Brunt-Väisälä frequ
 ency\; second\, the destabilization of the Kelvin-Helmholtz billows and th
 e gravitational instability lead to small-scale weakly stratified turbulen
 ce. We show that the anisotropic spectra at the maximum of dissipation sha
 re many characteristics with those obtained from numerical simulations of 
 forced stratified turbulence and from measurements in the atmosphere and i
 n the ocean.
LOCATION:MR2\, Centre for Mathematical Sciences\, Wilberforce Road\, Cambr
 idge
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