Combined role of molecular diffusion, mean streaming and helicity in the eddy diffusivity of short-correlated random flows

• Type: Article in International Scientific Journal
• Date: 2016-10

Authors

Marco Martins Afonso (Author) FCUP; Andrea Mazzino (Author) Other; Sílvio Gama (Author) FCUP

Journal

Title: Journal of Statistical Mechanics: Theory and Experiment

Vol. 2016 No. 10

Pages: 1-103205

ISSN: 1742-5468

Publisher: Institute of Physics Publishing

Indexing

ISI Web of Knowledge - 3 Citations

Scopus - 4 Citations

Other information

Authenticus ID: P-00M-52C

DOI: 10.1088/1742-5468/2016/10/103205

Abstract (EN): We analytically investigate the effective-diffusivity tensor of a tracer particle in a fluid flow endowed with a short correlation time. By means of functional calculus and a multiscale expansion, we write down the main contributions to the eddy diffusivity due to each single physical effect and to their interplays. Namely, besides molecular diffusivity and a constant uniform mean streaming, we take into account the possibility for the (incompressible, Gaussian, stationary, homogeneous, isotropic) turbulent fluctuations to break parity invariance. With respect to the classical turbulence-driven diffusivity amplification for delta-correlated flows, we find that the presence of a short temporal correlation induces a diminution even when coupled with such effects, with two principal exceptions. Notably, the diffusivity is-perturbatively-enlarged not only by the helical contribution itself, but also by the interference between molecular diffusion and mean flow.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 17