Anomalous diffusion and transport by a reciprocal convective flow

TL;DR

This paper investigates how reciprocal convective flows can cause anomalous diffusion and transport phenomena, including anisotropic diffusion and net shifts, through numerical simulations and theoretical analysis.

Contribution

It provides a detailed analysis of cooperative convection-diffusion effects under low-Reynolds-number conditions, revealing new anomalous transport behaviors.

Findings

Anisotropic diffusion observed under reciprocal flow.

Net shift in particle position due to flow.

Diffusion enhancement confirmed by simulations.

Abstract

Under low-Reynolds-number conditions, dynamics of convection and diffusion are usually considered separately because their dominant spatial and temporal scales are different, but cooperative effects of convection and diffusion can cause diffusion enhancement [Koyano et al., Phys. Rev. E, 102, 033109 (2020)]. In this study, such cooperative effects are investigated in detail. Numerical simulations based on the convection-diffusion equation revealed that anisotropic diffusion and net shift as well as diffusion enhancement occur under a reciprocal flow. Such anomalous diffusion and transport are theoretically derived by the analyses of the Langevin dynamics.