Intermittency, cascades and thin sets in three-dimensional Navier-Stokes turbulence

TL;DR

This paper explores the geometric structures of intermittency in 3D Navier-Stokes turbulence, linking thin filamentary sets to energy cascades and analyzing how solutions evolve across different dimensions.

Contribution

It investigates the association of weak solutions with energy cascades and infinite inverse length scales, revealing convergence and dimensional scaling properties.

Findings

Weak solutions are linked to energy cascades and finite inverse length scales.

Thin filamentary sets are key to understanding intermittency manifestations.

Solutions tend to evolve towards the smoothest, most dissipative class.

Abstract

Visual manifestations of intermittency in computations of three dimensional Navier-Stokes fluid turbulence appear as the low-dimensional or `thin' filamentary sets on which vorticity and strain accumulate as energy cascades down to small scales. In order to study this phenomenon, the first task of this paper is to investigate how weak solutions of the Navier-Stokes equations can be associated with a cascade and, as a consequence, with an infinite sequence of inverse length scales. It turns out that this sequence converges to a finite limit. The second task is to show how these results scale with integer dimension $D=1,\,2,\,3$ and, in the light of the occurrence of thin sets, to discuss the mechanism of how the fluid might find the smoothest, most dissipative class of solutions rather than the most singular.