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SUMMARY:The Destabilising Effect of Stratification in Layered Shear Flows 
 - Caulfield ( C (Cambridge)
DTSTART:20120510T103000Z
DTEND:20120510T113000Z
UID:TALK37688@talks.cam.ac.uk
CONTACT:Catherine Pearson
DESCRIPTION:Layered stratified flows\, where relatively deep regions of we
 ak (statically stable) stratification are separated by thinner interfacial
  layers of substantially stronger density gradient are commonly observed i
 n nature. If such flows are subjected to vertical shear\, it is well-known
  that a wide range of qualitatively different instabilities may develop. F
 or example\, the three-layer\, two interface case is susceptible to a `Tay
 lor' instability which\, although superficially similar to the classic Kel
 vin-Helmholtz instability\, is actually qualitatively different in its gro
 wth mechanism. The investigation of the nonlinear dynamics of this instabi
 lity\, and to a lesser extent the single-interface `Holmboe' instability\,
  (characterized in the nonlinear regime by cusped waves on the interface i
 nduced by propagating vortices) has proved difficult\, as the need to reso
 lve the associated sharp density gradients places heavy demands on the req
 uired numerical resolutions for simulation. However\, I show that it is po
 ssible to gain insight into the key nonlinear dynamics of such layered str
 atified shear flows by generalizing a reduced matched asymptotic `vorticit
 y defect' model (originally due to Balmforth\, Del Castillo-Negrete and Yo
 ung) to include the dynamical effects of density variations. I particularl
 y focus on investigating the finite amplitude structure of the saturated p
 rimary Taylor instability\, and the properties of the secondary instabilit
 ies to which Taylor and Holmboe instabilities are susceptible.
LOCATION:Open Plan Area\, BP Institute\, Madingley Rise CB3 0EZ
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