Berlin 2018 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 67: Poster: Active Matter, Microswimmers
DY 67.5: Poster
Thursday, March 15, 2018, 15:30–18:00, Poster A
Collective Dynamics of Squirmers in Poiseuille Flow — •Shahajhan Sorathiya and Holger Stark — Institut für Theoretische Physik, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany.
Bacteria in microfluidic Poiseuille flow show interesting collective dynamics such as pronounced centerline depletion [1]. We conduct a parametric study using the squirmer microswimmer model and multi-particle collision dynamics by varying squirmer volume fraction (C), the ratio of fluid flow strength (vf) to squirmer swimming speed (v0), and squirmer type β.
The most pronounced feature is a global axial polar order, which develops since squirmers collectively swim upstream against the flow.
At vf/v0 = 1 it is highest for neutral squirmers and also increases with
volume fraction
C. Pushers show the least polar order
while the alignment of pullers lies in between. For large flow speeds vf/v0 > 1 ,
alignment
against the flow decreases strongly
for all three squirmer types due to the onset of tumbling [2].
In parallel, for vf/v0 = 1 the axial velocity profiles of pullers and neutral squirmers are directed against the
fluid flow, while for vf/v0 = 4 the profiles of all squirmers are identical and directed with the fluid flow.
Finally, the lateral
density profiles
for neutral and puller squirmers
reveal enrichment in the channel center at all speed ratios and C < 20%, while pusher squirmers
develop increased density in the center for vf/v0 > 1.
[1] R. Rusconi, J. S. Guasto, and R. Stocker, Nature Phys. 10, 212
(2014).
A. Zöttl and H. Stark, Phys. Rev. Lett 108, 218104 (2012).