Swimming Dynamics Near a Wall in a Weakly Elastic Fluid

Abstract

We present a fully resolved solution of a low-Reynolds-number two- dimensionalmicroswimmerinaweaklyelasticfluidnearano-slipsurface.Theresults illustrate that elastic properties of the background fluid dramatically alter the swim- ming hydrodynamics and, depending on the initial position and orientation of the microswimmer, its residence time near the surface can increase by an order of magni- tude. Elasticity of the extracellular polymeric substance secreted by microorganisms canthereforeenhancetheiradhesionrate.Thedynamicalsystemisexaminedthrougha phase portrait in the swimming orientation and distance from the wall for four types of self-propulsionmechanisms,namely:neutralswimmers,pullers,pushers,andstirrers. The time-reversibility of the phase portraits breaks down in the presence of polymeric materials. The elasticity of the fluid leads to the emergence of a limit cycle for pullers and pushers and the change in type of fixed points from center to unstable foci for a microswimmer adjacent to a no-slip boundary.