Diffusion and dispersion of passive tracers: Navier-Stokes vs. MHD turbulence
Diffusion and dispersion of passive tracers: Navier-Stokes vs. MHD turbulence
A comparison of turbulent diffusion and pair-dispersion in homogeneous, macroscopically isotropic Navier-Stokes (NS) and nonhelical magnetohydrodynamic (MHD) turbulence based on high-resolution direct numerical simulations is presented. Significant differences between MHD and NS systems are observed in the pair-dispersion properties, in particular a strong reduction of the separation velocity in MHD turbulence as compared to the NS case. It is shown that in MHD turbulence the average pair-dispersion is slowed down for ?d lesssim t lesssim 10?d, ?d being the Kolmogorov time, due to the alignment of the relative Lagrangian tracer velocity with the local magnetic field. Significant differences in turbulent single-particle diffusion in NS and MHD turbulence are not detected. The fluid particle trajectories in the vicinity of the smallest dissipative structures are found to be characteristically different although these comparably rare events have a negligible influence on the statistics investigated in this work
14003-[5pp]
Müller, W.-C.
5516e747-008e-49d9-912f-942b668fa1a0
Busse, A.
0430b320-341b-4c73-9cb5-f35632d562a4
April 2007
Müller, W.-C.
5516e747-008e-49d9-912f-942b668fa1a0
Busse, A.
0430b320-341b-4c73-9cb5-f35632d562a4
Müller, W.-C. and Busse, A.
(2007)
Diffusion and dispersion of passive tracers: Navier-Stokes vs. MHD turbulence.
Europhysics Letters, 78 (1), .
(doi:10.1209/0295-5075/78/14003).
Abstract
A comparison of turbulent diffusion and pair-dispersion in homogeneous, macroscopically isotropic Navier-Stokes (NS) and nonhelical magnetohydrodynamic (MHD) turbulence based on high-resolution direct numerical simulations is presented. Significant differences between MHD and NS systems are observed in the pair-dispersion properties, in particular a strong reduction of the separation velocity in MHD turbulence as compared to the NS case. It is shown that in MHD turbulence the average pair-dispersion is slowed down for ?d lesssim t lesssim 10?d, ?d being the Kolmogorov time, due to the alignment of the relative Lagrangian tracer velocity with the local magnetic field. Significant differences in turbulent single-particle diffusion in NS and MHD turbulence are not detected. The fluid particle trajectories in the vicinity of the smallest dissipative structures are found to be characteristically different although these comparably rare events have a negligible influence on the statistics investigated in this work
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Published date: April 2007
Organisations:
Aerodynamics & Flight Mechanics Group
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Local EPrints ID: 337397
URI: http://eprints.soton.ac.uk/id/eprint/337397
PURE UUID: 6f8442d5-2b1a-43e6-a3cf-a43c8a2a159d
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Date deposited: 12 Sep 2012 13:20
Last modified: 14 Mar 2024 10:53
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Author:
W.-C. Müller
Author:
A. Busse
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