Regensburg 2022 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 31: Active Matter 4 (joint session DY/BP/CPP)
DY 31.3: Vortrag
Mittwoch, 7. September 2022, 15:30–15:45, H18
Optimal turbulent transport in microswimmer suspensions — •Henning Reinken1, Sabine H. L. Klapp1, and Michael Wilczek2 — 1Technische Universität Berlin — 2Universität Bayreuth
Microwsimmer suspensions, a paradigmatic example of an active fluid, self-organize into complex spatio-temporal flow patterns, including regular vortex lattices and mesoscale turbulence.
This work investigates the transport properties of these suspensions by tracking the diffusive motion of passive tracers in the turbulent flow.
We apply a continuum model for the effective microswimmer velocity field [1,2],
where the dynamics is governed by the competition between relaxation
to a regular vortex lattice and destabilization by nonlinear advection.
Varying the strength of nonlinear advection, we observe two qualitatively different regimes of flow transport that we distinguish with the help of the dimensionless Kubo number K, which compares different time scales.
Right above the transition to turbulence, the flow field evolves very slowly (K ≫ 1) and the spatial vortex structures lead to dominant trapping effects.
In contrast, for large advection strength, much faster dynamics (K ≪ 1) leads to transport properties completely determined by the temporal correlations of the flow.
In between (K ≈ 1), we observe a regime of optimal transport, where the diffusion coefficient reaches a maximum.
[1] Reinken, Klapp, Bär, Heidenreich, Phys. Rev. E 97, 022613 (2018)
[2] James, Bos, Wilczek, Phys. Rev. Fluids
3, 061101(R) (2018).