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SUMMARY:On the origin of the vorticity alignment in homogeneous and isotro
 pic turbulence - Takeshi Matsumoto (Kyoto University)
DTSTART:20240611T130000Z
DTEND:20240611T135000Z
UID:TALK214684@talks.cam.ac.uk
DESCRIPTION:Co-Author: Yoshifumi Kimura (Graduate School of Mathematics\, 
 Nagoya University)\nIt is known that\, in incompressible homogeneous and i
 sotropic Navier-Stokes turbulence\, the vorticity vector tends to align wi
 th the eigenvector corresponding to the intermediate eigenvalue of the rat
 e-of-strain tensor. This phenomenon\, known as vorticity alignment\, repre
 sents a remarkable orientational order in the fully developed random field
 . Since its discovery in a direct numerical simulation (DNS) by Ashurst et
  al. (1987)\, various scenarios for this alignment have been proposed. How
 ever\, its precise mechanism remains elusive.In this study\, we propose to
  describe the alignment property using local spherical coordinates defined
  by the eigen-directions (principal axes) of the rate-of-strain tensor. Us
 ing these coordinates we revisit the three-dimensional structure of the al
 ignment property. This revision leads us to develop a dynamical-system mod
 el to describe the orientation of the vorticity. We then show that the vor
 ticity alignment in question corresponds to a quasi-equilibrium point of t
 he model. Lastly\, returning to DNS\, we statistically analyse vortical st
 ructures in the local coordinates to identify the structure responsible fo
 r the vorticity alignment.
LOCATION:Seminar Room 1\, Newton Institute
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