Extraction and tracking of multi-scaled vortices from a homogeneous isotropic turbulent field

Abstract

Vortex structures of various scales are extracted from an isotropic homogeneous turbulent field, and they are tracked. By filtering the flow field using Fourier decomposition and removing the fragments of small volumes, three flow fields, namely the large, intermediate and fine, each containing vortices of similar scales are obtained. Also, an automatic vortex-tracking scheme that can handle the vortex division is presented. By comparing the vortex structures found in flow fields of various scales, it is shown that vortex structures are more actively stretching in the fine-scale flow field compared to the larger-scale flow fields. By tracking the vortex structures in flow fields of various scales, it is shown that vortex structures in the large-scale flow field have a tendency to stretch when vortex division into smaller pieces is taking place, though such a tendency cannot be found among the vortex structures of smaller-scale flow fields. The division process is found to be slower for the vortex structures of the smaller-scale flow fields.