Point-vortex model for Lagrangian intermittency in turbulence.
Experiments have shown that Lagrangian statistics in turbulent flows display Gaussianly distributed velocity values and non-Gaussianly distributed velocity differences or accelerations. Coherent flow structures in the form of vortices have often been proposed to play an important role in this behavior. Here we examine the origin of these statistics using both continuously stirred n -body point-vortex simulations and analytic random variable transformation in a simplified model of randomly distributed vortices. We conclude that Lagrangian velocity distributions can be understood in terms of dominant nearest vortex neighbor contributions. Accelerations likewise reflect vortical contributions, but at smallest temporal increment are dominated, not by the motion of the Lagrangian tracers, but by vorticity reconfiguration within the domain.
Rast
Mark Peter
MP
Laboratory for Atmospheric and Space Physics and Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, Colorado 80309, USA.
Pinton
Jean-Francois
JF