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Eddy diffusivities in scalar transport

L. Biferale·A. Crisanti·M. Vergassola·A. Vulpiani
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Abstract

Standard and anomalous transport in incompressible flow is investigated using multiscale techniques. Eddy-diffusivities emerge from the multiscale analysis through the solution of an auxiliary equation. From the latter it is derived an upper bound to eddy-diffusivities, valid for both static and time-dependent flow. The auxiliary problem is solved by a perturbative expansion in powers of the Péclet number resummed by Padé approximants and by a conjugate gradient method. The results are compared to numerical simulations of tracers dispersion for three flows having different properties of Lagrangian chaos. It is shown on a concrete example how the presence of anomalous diffusion can be revealed from the singular behaviour of the eddy-diffusivity at very small molecular diffusivities.

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L. Biferale, A. Crisanti, M. Vergassola, A. Vulpiani. 1994-12-28. Eddy diffusivities in scalar transport. https://doi.org/10.1063/1.868651

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