Diffusion and dispersion of passive tracers: Navier-Stokes vs. MHD turbulence

作者：Mueller W C; Busse A

来源：EPL, 2007, 78(1): 14003.

DOI：10.1209/0295-5075/78/14003

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. Signicant 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 tau(d) less than or similar to t less than or similar to 10 tau(d), tau(d) being the Kolmogorov time, due to the alignment of the relative Lagrangian tracer velocity with the local magnetic field. Signicant 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.

• 出版日期2007