Intermittent vortex structures in homogeneous isotropic turbulence

Abstract

ALTHOUGH well developed turbulence exhibits complex, chaotic spatial and temporal behaviour, there is much experimental evidence to suggest that a remarkable degree of coherence is also present¹. It is known² that correlations in small-scale turbulent motions show significant deviations from the gaussian statistics usually expected for large, randomly interacting systems. This phenomenon, known as intermittency, has long resisted analytical description because of the lack of a simple, universal characterization of turbulence structures³. Here we report numerical simulations which show that there are remarkably simple spatial structures associated with intermittent regions of vorticity. In particular, in contrast to the classical description of turbulence as an array of 'pancake'- or 'lasagne'-like eddies⁴, we find that high-amplitude vortex structures are tube-like and that they generate local velocity fields that spiral around them.