Pair dispersion in dilute suspension of active swimmers
Author(s)
Belan, Sergey; Kardar, Mehran
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Ensembles of biological and artificial microswimmers produce long-range velocity fields with strong nonequilibrium fluctuations, which result in a dramatic increase in diffusivity of embedded particles (tracers). While such enhanced diffusivity may point to enhanced mixing of the fluid, a rigorous quantification of the mixing efficiency requires analysis of pair dispersion of tracers, rather than simple one-particle diffusivity. Here, we calculate analytically the scale-dependent coefficient of relative diffusivity of passive tracers embedded in a dilute suspension of run-and-tumble microswimmers. Although each tracer is subject to strong fluctuations resulting in large absolute diffusivity, the small-scale relative dispersion is suppressed due to the correlations in fluid velocity which are relevant when the inter-tracer separation is below the persistence length of the swimmer's motion. Our results suggest that the reorientation of swimming direction plays an important role in biological mixing and should be accounted in the design of potential active matter devices capable of effective fluid mixing at microscale.
Date issued
2019-02Department
Massachusetts Institute of Technology. Department of PhysicsJournal
Journal of Chemical Physics
Publisher
American Institute of Physics (AIP)
Citation
Belan, Sergey and Mehran Kardar. “Pair Dispersion in Dilute Suspension of Active Swimmers.” The Journal of Chemical Physics 150, 6 (February 2019): 064907 © 2019 Author(s)
Version: Author's final manuscript
ISSN
0021-9606
1089-7690
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