Non-universal velocity probability densities in two-dimensional turbulence: the effect of large-scale dissipation

Abstract

We show that some statistical properties of forced two-dimensional turbulence have an important sensitivity to the form of large-scale dissipation which is required to damp the inverse cascade. We consider three models of large-scale dissipation: linear "Ekman" drag, non-linear quadratic drag, and scale selective hypo-drag that damps only low-wavenumber modes. In all cases, the statistically steady vorticity field is dominated by almost axisymmetric vortices, and the probability density function of vorticity is non-Gaussian. However, in the case of linear and quadratic drag, we find that the velocity statistics is close to Gaussian, with non-negligible contribution coming from the background turbulent flow. On the other hand, with hypo-drag, the probability density function of velocity is non-Gaussian and is predominantly determined by the properties of the vortices. With hypo-drag, the relative positions of the vortices and the exponential distribution of the vortex extremum are important factors responsible for the non-Gaussian velocity statistics.

References in corpus (7)

• Hyperviscosity, Galerkin truncation and bottlenecks in turbulence
• Lagrangian Dynamics in High-Dimensional Point-Vortex Systems
• Intermittency in two-dimensional Ekman-Navier-Stokes turbulence
• Intermittency in Two-Dimensional Turbulence with Drag
• The statistics of velocity fluctuations arising from a random distribution of point vortices: the speed of fluctuations and the diffusion coefficient
• On the probability distribution of power fluctuations in turbulence
• Energy-Enstrophy Stability of beta-plane Kolmogorov Flow with Drag

Cited by in corpus (3)

• The vortex gas scaling regime of baroclinic turbulence
• Kolmogorovian active turbulence of a sparse assembly of interacting swimmers
• Fractional Laplacian Spectral Approach to Turbulence in a Dusty Plasma Monolayer