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SUMMARY:Vortex simulations of 2D turbulence in confined domains - Macaskil
 l\, C (Sydney)
DTSTART:20081210T113000Z
DTEND:20081210T120000Z
UID:TALK15608@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:This talk considers the evolution of 2D turbulence in a confin
 ed domain with slip boundary conditions imposed. Several domain shapes are
  considered\, both regular (e.g. a circle\, a square) and irregular (e.g. 
 random coastlines). The CASL (Contour-Advective Semi-Lagrangian) technique
  is employed\, taking as the initial condition a random assembly of vortex
  patches.\n\nIt is known that the initial angular momentum is important in
  determining whether the very long time state is dipolar or monopolar when
  no-slip boundary conditions are considered. Although this is not the case
  for slip boundary conditions\, the initial total circulation plays a simi
 lar role. We explore the dependence of the final state on the initial circ
 ulation for a range of geometries. Some examples are shown where trapping 
 of vortices in 'bays'\, caused by domain-scale interactions\, can influenc
 e the long time evolution.\n\nRecent work on 2D turbulence in a periodic b
 ox has shown how the rate of dipole/monopole interactions can be related t
 o the time rate of decay of enstrophy at intermediate to long times (once 
 the initial very strong interactions are over). The presence of the domain
  boundary provides a mechanism for enhancing the rate of such interactions
 \, as monopoles of opposite sign tend to hug the boundaries\, travel in op
 posite directions and then meet to form dipoles which are then launched in
 to the flow. Accordingly\, we consider the effect of domain shape on the f
 requency of dipole formation and dipole/monopole interactions and the corr
 esponding rate of decay of enstrophy. Finally\, we discuss extensions of t
 his work to the 3D quasi-geostrophic case. 
LOCATION:Seminar Room 1\, Newton Institute
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