Strong effect of weak diffusion on scalar turbulence at large scales
Abstract
Passive scalar turbulence forced steadily is characterized by the velocity correlation scale L, injection scale l, and diffusive scale r_{d}. The scales are well separated if the diffusivity is small, r_{d}≪l,L, and one normally says that effects of diffusion are confined to smaller scales, r ≪r_{d}. However, if the velocity is single scale, one finds that a weak dependence of the scalar correlations on the molecular diffusivity persists to even larger scales, e.g., l ≫r≫r_{d} (E. Balkovsky et al., Pis'ma Zh. Eksp. Teor. Fiz. 61, 1012 (1995) [JETP Lett. 61, 1049 (1995)]). We consider the case of L ≫l and report a counterintuitive result, namely the emergence of a new range of large scales, L ≫r≫l^{2}/r_{d}, where the diffusivity shows a strong effect on scalar correlations.
 Publication:

Physics of Fluids
 Pub Date:
 October 2007
 DOI:
 10.1063/1.2793145
 arXiv:
 arXiv:0706.2928
 Bibcode:
 2007PhFl...19j1703C
 Keywords:

 47.27.tb;
 47.10.g;
 Turbulent diffusion;
 General theory in fluid dynamics;
 Nonlinear Sciences  Chaotic Dynamics
 EPrint:
 4 pages, 1 figure, submitted to Physics of Fluids