DOI: 10.1615/THMT-18
ISBN Print: 978-1-56700-468-7
ISBN Online: 978-1-56700-467-0
ISSN Print: 2377-2816
The Local Vorticity Signature of Vortex Structures
SINOPSIS
Vortex identification is a central problem in the structural approach to turbulence, where vortical structures are used to model important statistical features of the turbulent velocity field. However, even the most popular two-dimensional vortex identification method, known as the "swirling strength criterion", turns out to be affected by problematic issues, essentially related to the use of nonlocal vorticity kernels. We propose an alternative criterion, coined as the "λω-criterion", which is based on the local curvature properties of the vorticity graph, and is shown to perform generally better than the swirling strength criterion for a large number of controlled Monte Carlo tests and for the analysis of a numerical turbulent channel flow. In the latter, the λω-criterion indicates, for the first time within the structural framework, the existence of small scale isotropic turbulent fluctuations in the logarithmic layer, as long ago addressed in boundary layer phenomenology.