INTERMITTENT VORTEX STRUCTURES IN HOMOGENEOUS ISOTROPIC TURBULENCE

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. © 1990 Nature Publishing Group.