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SUMMARY:Large-scale structure formation by turbulent kinetic helicity - No
 bumitsu Yokoi (University of Tokyo)
DTSTART:20240411T150000Z
DTEND:20240411T160000Z
UID:TALK215386@talks.cam.ac.uk
DESCRIPTION:Local density of turbulent kinetic helicity\, defined by the c
 orrelation between velocity and vorticity\, is a measure of breakage of mi
 rror-symmetry and provides structural information of turbulence. With the 
 aid of a closure theory for inhomogeneous\, anisotropic\, and non-equilibr
 ium turbulence: multiple-scale renormalised perturbation expansion theory\
 , inhomogeneous rotating turbulence is investigated. The analytical expres
 sion for the Reynolds stress and vortex-motive (or ponderomotive) force is
  derived from the fundamental equations. This expression includes the inho
 mogeneous helicity coupled with the mean absolute vorticiy (the anti-symme
 tric part of mean shear) as well as the usual eddy viscosity coupled with 
 the mean velocity strain (the symmetric part of mean shear). The validity 
 of this expression is confirmed through applications of the turbulence mod
 el to turbulent swirling flow in a pipe\, and direct numerical simulations
  of a rotating box turbulence with inhomogeneous turbulent helicity inject
 ed by external forcing. Several possible applications to the geophysical a
 nd astrophysical turbulent flows will be presented\, followed by some prop
 osals for the subgrid-scale (SGS) turbulence modelling with structure effe
 cts incorporated through SGS turbulent helicity.
LOCATION:Seminar Room 2\, Newton Institute
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