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arXiv · 0706.2928

Strong effect of weak diffusion on scalar turbulence at large scales

M. Chertkov·I. Kolokolov·V. Lebedev
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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, $r_d\ll l,L$, and one normally says that effects of diffusion are confined to smaller scales, $r\ll r_d$. 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. $l\gg r\gg r_d$ \cite{95BCKL}. We consider the case of $L\gg l$ and report a counter-intuitive result -- the emergence of a new range of large scales, $L\gg r\gg l^2/r_d$, where the diffusivity shows a strong effect on scalar correlations.

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M. Chertkov, I. Kolokolov, V. Lebedev. 2007-06-20. Strong effect of weak diffusion on scalar turbulence at large scales. https://doi.org/10.1063/1.2793145

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