Solute dispersion in pre-turbulent confined active nematics

TL;DR

This paper studies how solutes disperse in active nematic fluids within narrow channels, revealing activity-dependent dispersion mechanisms in oscillatory and dancing flow regimes with potential applications.

Contribution

It uncovers the common dispersion mechanism driven by velocity moments in different pre-turbulent active nematic flows, highlighting activity's role in enhancing dispersion.

Findings

Dispersion is governed by velocity second moments and activity.

Dispersion coefficient can increase up to tenfold over molecular diffusion.

Both flow regimes show enhanced dispersion with activity.

Abstract

We investigate the dispersion of solutes in active nematic fluids confined in narrow channels based on simulations of nematohydrodynamics. The study focuses on two pre-turbulent regimes: oscillatory flow, with net mass flux, and dancing flow, without net flux. Our findings reveal that the longitudinal dispersion of solutes, in both regimes, is determined by the second moments of the longitudinal and transverse components of the velocity field and proportional to the activity, suggesting a common mechanism for dispersion in these distinct flows. Finally, we found that the dispersion coefficient may increase up to one order of magnitude with respect to molecular diffusion in the dancing flow regime and that it is also enhanced in oscillatory flows, with potential for applications in natural biological environments and engineered devices.