2016/06/15 by Marco Martins Afonso, Andrea Mazzino, Sílvio Gama
Biochemistry, Genetics and Molecular Biology · Engineering · Physics and Astronomy · #Diffusion #Diffusion and Search Dynamics #Eddy diffusion #Flow (mathematics) #Fluid Dynamics and Turbulent Flows #Helicity #Mass diffusivity #Molecular diffusion #Particle Dynamics in Fluid Flows #Thermal diffusivity #Turbulence #nlin.CD #physics.flu-dyn
paper · pdf · doi:10.1088/1742-5468/2016/10/103205
published as Journal of Statistical Mechanics: Theory and Experiment, 103205, pp. 1-17 (10\)(2016) · 14 pages, submitted to J.Stat.Mech
arxiv created 2016/06/15 · openalex created_date 2016/06/24 · openalex publication_date 2016/10/19 · arxiv updated 2016/10/24 · openalex updated_date 2026/08/05
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.