Dresden 2017 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 45: Microswimmers (joint session BP/DY)

DY 45.5: Talk

Thursday, March 23, 2017, 12:15–12:30, ZEU 250

Dynamics of spheroidal squirmers in Poiseuille flow — •Hemalatha Annepu, Mario Theers, Gerhard Gompper, and Roland G. Winkler — Theoretical Soft Matter and Biophysics, Institute for Advanced Simulation and Institute of Complex Systems, Forschungszentrum Jülich, 52425 Jülich, Germany

Bacteria such as E. coli exhibit a remarkable rheological behavior. On the one hand, the viscosity exhibits a Newtonian plateau at low shear rates, which decreases with increasing concentration. On the other hand, the bacteria exhibit positive rheotaxis, i.e., they swim preferentially upstream next to surfaces. This points toward an intriguing interplay between the swimmer flow field with the surface. To analyze the properties of microswimmers in channel flows, we consider spheriodal squirmers with a rotlet dipole embedded in a MPC fluid and study their flow-induced structure and dynamics. The no-slip boundary condition at a surface combined with the swimmer characteristics (puller, pusher) leads to a preferential alignment parallel (pusher) or perpendicular (puller) to the wall. This applies to both, spherical as well as spheroidal squirmers as long as they are not to close to a surface and the hydrodynamics is determined by the far field. We want to shed light on the influence of near-field hydrodynamic interactions on the swimming behavior of spheroidal squirmers close to surfaces. Our simulations reveal a dependence of the swimming behavior under flow on the shape of the microswimmer. We find positive rheotaxis for spheroidal pushers in narrow channels, which disappears in the limit of zero rotlet dipole strength.