Enhanced active swimming in viscoelastic fluids
Department of Applied Mathematics and Theoretical Physics, University of Cambridge - Cambridge CB3 0WA, UK
Received: 8 September 2014
Accepted: 7 October 2014
Swimming microorganisms often self-propel in fluids with complex rheology. While past theoretical work indicates that fluid viscoelasticity should hinder their locomotion, recent experiments on waving swimmers suggest a possible non-Newtonian enhancement of locomotion. We suggest a physical mechanism, based on fluid-structure interaction, leading to swimming in a viscoelastic fluid at a higher speed than in a Newtonian one. Using Taylor's two-dimensional swimming sheet model, we solve for the shape of an active swimmer as a balance between the external fluid stresses, the internal driving moments, and the passive elastic resistance. We show that this dynamic balance leads to a generic transition from hindered rigid swimming to enhanced flexible locomotion. The results are physically interpreted as due to a viscoelastic suction increasing the swimming amplitude in a non-Newtonian fluid and overcoming viscoelastic damping.
PACS: 47.63.Gd – Swimming microorganisms / 47.63.-b – Biological fluid dynamics / 47.50.-d – Non-Newtonian fluid flows
© EPLA, 2014