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arXiv:astro-ph/0306521 (astro-ph)
[Submitted on 25 Jun 2003 (v1), last revised 10 Mar 2004 (this version, v3)]

Title:Non-Fickian diffusion and tau approximation from numerical turbulence

Authors:Axel Brandenburg (Nordita), Petri Käpylä (KIS, Oulu), Amjed Mohammed (Oldenburg)
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Abstract: Evidence for non-Fickian diffusion of a passive scalar is presented using direct simulations of homogeneous isotropic turbulence. The results compare favorably with an explicitly time-dependent closure model based on the tau approximation. In the numerical experiments three different cases are considered: (i) zero mean concentration with finite initial concentration flux, (ii) an initial top hat profile for the concentration, and (iii) an imposed background concentration gradient. All cases agree in the resulting relaxation time in the tau approximation relating the triple correlation to the concentration flux. The first order smoothing approximation is shown to be inapplicable.
Comments: 10 pages, 7 figs, Physics of Fluids (final version)
Subjects: Astrophysics (astro-ph); Chaotic Dynamics (nlin.CD); Fluid Dynamics (physics.flu-dyn)
Report number: NORDITA 2003-34 AP
Cite as: arXiv:astro-ph/0306521
  (or arXiv:astro-ph/0306521v3 for this version)
  https://doi.org/10.48550/arXiv.astro-ph/0306521
Journal reference: Phys.Fluids 16:1020-1027,2004
Related DOI: https://doi.org/10.1063/1.1651480

Submission history

From: Axel Brandenburg [view email]
[v1] Wed, 25 Jun 2003 18:19:13 UTC (312 KB)
[v2] Sat, 31 Jan 2004 20:23:37 UTC (169 KB)
[v3] Wed, 10 Mar 2004 03:45:32 UTC (169 KB)
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