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.
Keywords
Cite
@article{arxiv.1703.07000,
title = {Non-universal velocity probability densities in two-dimensional turbulence: the effect of large-scale dissipation},
author = {Yue-Kin Tsang},
journal= {arXiv preprint arXiv:1703.07000},
year = {2017}
}