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SUMMARY:Three-dimensional stability of a horizontally sheared flow in a st
 ably stratified fluid - Chomaz\, JM (LadHyX)
DTSTART:20081212T143000Z
DTEND:20081212T150000Z
UID:TALK15615@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:This work investigates the three-dimensional stability of a ho
 rizontal flow sheared horizontally\, the hyperbolic tangent velocity profi
 le\, in a stably stratified fluid. In an homogeneous fluid\, the Squire th
 eorem states that the most unstable perturbation is two-dimensional. When 
 the flow is stably stratified\, this theorem does not apply and we have pe
 rformed a numerical study to investigate the three-dimensional stability c
 haracteristics of the flow. When the Froude number\, Fh\, is varied from 
 ∞ to 0.05\, the most unstable mode remains two-dimensional. However\, th
 e range of unstable vertical wavenumbers widens proportionally to the inve
 rse of the Froude number for Fh 1. This means that the stronger the strati
 fication\, the smaller the vertical scales that can be destabilized. This 
 loss of selectivity of the two-dimensional mode in horizontal shear flows 
 stratified vertically may explain the layering observed numerically and ex
 perimentally. Extension to transient and nonlinear behaviour are presented
 .
LOCATION:Seminar Room 1\, Newton Institute
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