Spatial extreme values of vorticity and velocity gradients in two-dimensional turbulent flows

TL;DR

This paper investigates the statistical behavior of extreme vorticity and velocity gradients in two-dimensional turbulent flows, revealing non-Gaussian distributions and the conditions under which Gumbel distributions apply.

Contribution

It provides a detailed analysis of the distribution of spatial extrema in 2D turbulence and compares them with truncated Euler equations, highlighting differences in extreme value behaviors.

Findings

Extrema follow non-Gaussian distributions in turbulence.

Gumbel distribution describes extrema in truncated Euler equations.

Vorticity extrema are located at vortex cores, gradients at vortex edges.

Abstract

We study the distribution of spatial extrema of vorticity and the determinant of the strain rate tensor for a two-dimensional turbulent flow forced by a Kolmogorov forcing. The distribution of these quantities follow non-Gaussian behaviour and they do not fall into the Generalised Extreme value distributions. It is found that for the truncated Euler equations the spatial extrema of vorticity and strain rate tensor are well described by the Gumbel distribution. The spatial extrema for the vorticity is found to be at the core of the vortices while the velocity gradients are found near the edges of the vortices or at the shear layers in the regions between the vortices. Temporal correlations of the velocity gradients shed light on the extreme value distributions obtained for turbulence and the truncated Euler equations.