Flagellar swimming in viscoelastic fluids

9 Jul 2018, 11:00
30m
New Law School---106 (University of Sydney)

New Law School---106

University of Sydney

100
Oral Presentation Minisymposium: From solitary swimmers to coordinated groups: modelling motion in fluids at very low Reynolds number From solitary swimmers to coordinated groups: Modelling motion in fluids at very low Reynolds number

Speaker

Robert Guy (University of California Davis)

Description

Many important biological functions depend on microorganisms' ability to move in viscoelastic fluids such as mucus and wet soil. The effects of fluid elasticity on motility remain poorly understood partly because the swimmer strokes depend on the properties of the fluid medium, which obfuscates the mechanisms responsible for observed behavioural changes. We use experimental data on the gaits of Chlamydomonas reinhardtii swimming in Newtonian and viscoelastic fluids as inputs to numerical simulations that decouple the swimmer gait and fluid type in order to isolate the effect of fluid elasticity on swimming. In viscoelastic fluids, cells employing the Newtonian gait swim faster but generate larger stresses and use more power, and as a result the viscoelastic gait is more efficient. Furthermore, we show that fundamental principles of swimming based on viscous fluid theory miss important flow dynamics: fluid elasticity provides an elastic memory effect which increases both the forward and backward speeds, and (unlike purely viscous fluids) larger fluid stress accumulates around flagella moving tangent to the swimming direction, compared to the normal direction.

Primary authors

Robert Guy (University of California Davis) Chuanbin Li (Pennsylvania State University) Qin Boyang (University of Pennsylvania) Arvind Gopinath (University of California Merced) Arratia Paulo (University of Pennsylvania) Becca Thomases (University of California Davis)

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