Seminar series
Date
Thu, 31 Oct 2013
Time
16:00 -
17:00
Location
L3
Speaker
George Haller
Organisation
(ETH) Zurich
We discuss a simple variational principle for coherent material vortices
in two-dimensional turbulence. Vortex boundaries are sought as closed
stationary curves of the averaged Lagrangian strain. We find that
solutions to this problem are mathematically equivalent to photon spheres
around black holes in cosmology. The fluidic photon spheres satisfy
explicit differential equations whose outermost limit cycles are optimal
Lagrangian vortex boundaries. As an application, we uncover super-coherent
material eddies in the South Atlantic, which yield specific Lagrangian
transport estimates for Agulhas rings. We also describe briefly coherent
Lagrangian vortex detection to three-dimensional flows.