Journal of Fluid Mechanics



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On the relationships between local vortex identification schemes


PINAKI CHAKRABORTY a1, S. BALACHANDAR a1 and RONALD J. ADRIAN a1
a1 Department of Theoretical and Applied Mechanics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA

Article author query
chakraborty p   [Google Scholar] 
balachandar s   [Google Scholar] 
adrian rj   [Google Scholar] 
 

Abstract

We analyse the currently popular vortex identification criteria that are based on point-wise analysis of the velocity gradient tensor. A new measure of spiralling compactness of material orbits in vortices is introduced and using this measure a new local vortex identification criterion and requirements for a vortex core are proposed. The inter-relationships between the different criteria are explored analytically and in a few flow examples, using both zero and non-zero thresholds for the identification parameter. These inter-relationships provide a new interpretation of the various criteria in terms of the local flow kinematics. A canonical turbulent flow example is studied, and it is observed that all the criteria, given the proposed usage of threshold, result in remarkably similar looking vortical structures. A unified interpretation based on local flow kinematics is offered for when similarity or differences can be expected in the vortical structures educed using the different criteria.

(Published Online July 5 2005)
(Received February 10 2004)
(Revised February 9 2005)



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