Nonuniversal velocity probability densities in twodimensional turbulence: The effect of largescale dissipation
Abstract
We show that some statistical properties of forced twodimensional turbulence have an important sensitivity to the form of largescale dissipation, which is required to damp the inverse cascade. We consider three models of largescale dissipation: linear "Ekman" drag, nonlinear quadratic drag, and scaleselective hypodrag that damps only lowwavenumber modes. In all cases, the statistically steady vorticity field is dominated by almost axisymmetric vortices, and the probability density function of vorticity is nonGaussian. However, in the case of linear and quadratic drag, we find that the velocity statistics is close to Gaussian, with nonnegligible contribution coming from the background turbulent flow. On the other hand, with hypodrag, the probability density function of velocity is nonGaussian and is predominantly determined by the properties of the vortices. With hypodrag, the relative positions of the vortices and the exponential distribution of the vortex extremum are important factors responsible for the nonGaussian velocity statistics.
 Publication:

Physics of Fluids
 Pub Date:
 November 2010
 DOI:
 10.1063/1.3504377
 arXiv:
 arXiv:1703.07000
 Bibcode:
 2010PhFl...22k5102T
 Keywords:

 drag;
 exponential distribution;
 turbulence;
 vortices;
 47.27.E;
 47.32.y;
 02.50.Ng;
 Turbulence simulation and modeling;
 Vortex dynamics;
 rotating fluids;
 Distribution theory and Monte Carlo studies;
 Physics  Fluid Dynamics;
 Physics  Atmospheric and Oceanic Physics
 EPrint:
 Phys. Fluids 22, 115102 (2010)