(394h) Collective Motion in Viscoelastic Fluids

Swimming microorganisms and their collective motion have received growing attention for their importance in pathology, reproduction and ecology. The suspension of self-propelled microorganisms exhibits many turbulent-like behaviors, such as locally correlated motions, enhanced particle diffusion, and enhanced fluid mixing. Even though several studies have been conducted on the collective motion in a Newtonian fluid, the natural habitat of microorganisms is often non-Newtonian. The non-Newtonian fluid rheological properties, such as viscoelasticity of saliva, mucus and biofilm, significantly affect the swimming properties and hydrodynamic interaction of microorganisms. In this work, we use direct numerical simulation to investigate the collective motion of rod-like swimmers in viscoelastic fluids. We demonstrate that the fluid elasticity has different effects on a suspension of microswimmers compared to an isolated swimmer. It has a stronger effect on a suspension of pushers compared to pullers. The induced polymer stresses enhance the lateral attraction of pushers and break down the large scale fluid structures.