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SUMMARY:Internal gravity waves in the ocean: Global and local stability an
 alysis and computation of transient growth
DTSTART:20170207T141500
DTEND:20170207T151500
DTSTAMP:20260414T112055Z
UID:a15dca7d1598935e244fb253471023ed35d31d7839876513284df568
CATEGORIES:Conferences - Seminars
DESCRIPTION:Gaétan Lerisson\, LadHyx\, Ecole Polytechnique\, Paris France
 \nInternal gravity waves that exists in a linearly stratified fluid are pa
 rticularly important in the deep ocean. Generated at the bottom of oceans\
 , they transport energy over large distances. It is believed that their de
 stabilization enhances turbulent mixing\, a necessary ingredient to mainta
 in the meridional oceanic circulation and the deep oceanic stratification.
  Through fully non-linear and linear direct numerical simulations\, we sho
 w that the stability of a gravity wave beam\, and its transient growth int
 ensity\, strongly depend on the generation mechanism. This mechanism can b
 e described by a single control parameter : the horizontal mean flow. For 
 small mean flows\, small scale instabilities dominate\, as for internal ti
 des excited beams. For strong mean flows\, large scale instabilities domin
 ate as for Lee waves\; however\, small scales can dominate the short-times
  growth. By computing the linear impulse response of a monochromatic progr
 essive internal wave\, we propose an interpretation based on an absolute a
 nd convective theory applied to a 2D periodic flow. We show that most of t
 he unstable modes are well described by the classical triadic instability 
 theory\, despite being far from the ideal conditions of its application.\n
  
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STATUS:CONFIRMED
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