Self-propulsion of a freely suspended swimmer by a swirling tail in a viscoelastic fluid

Abstract

We consider a model microswimmer consisting of two counter-rotating spheres that has zero propulsion in a Newtonian fluid but swims in the direction of the larger sphere in a viscoelastic fluid. This is analogous to the bacteria E. coli which propels itself with a rotating flagellar bundle and counter-rotating cell body. We find that the swimmer's thrust is due to a pressure imbalance along its body resulting from polymeric hoop stresses around the faster spinning smaller sphere that advect fluid radially inward. In contrast to previous work, our artificial swimmer is both force- and torque-free. We show that the latter condition has a profound impact on the swimming speed in an elastic fluid.

Topics & Concepts