Dr Colm Connaughton
(Center for Nonlinear Studies, Los Alamos National Laboratory)

will speak on

The Spectra and Vortices of Two-dimensional Turbulence

Time: 2:15PM
Date: Mon 24th July 2006
Location: Mathematical Sciences Seminar Room [map]

Abstract: I will describe the physics of so-called "blocked inverse cascades" in
two dimensional turbulence. A blocked cascade occurs when the large scale
dissipation is too weak to dissipate all of the energy pumped into the
inverse
cascade before it reaches the size of the system. This blocking
facilitates the generation of very intense coherent vortices on the
scale of
the system which are qualitatively different to the vortices observed in
the
regular inverse cascade. They are stabilised by finite size effects and
as a result can become much more intense than regular vortices. They can
have
a strong impact on the energy spectrum and other "standard" turbulence
diagnostics. In particular the presence of these large scale vortices
tends to
replace the usual k^-5/3 energy spectrum with a k^-3 spectrum at the
largest
scales. I will make some speculations about where this mechanism for
stabilising
large scale vortices might have geophysical relevance.

(This talk is part of the Meteorology series.)

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