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arXiv · 1811.06959

Elastohydrodynamics of swimming helices: effects of flexibility and confinement

John LaGrone·Ricardo Cortez·Lisa Fauci
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Abstract

Motivated by bacterial transport through porous media, here we study the swimming of an actuated, flexible helical filament in both three-dimensional free space and within a cylindrical tube whose diameter is much smaller than the length of the helix. The filament, at rest, has a native helical shape modeled after the geometry of a typical bacterial flagellar bundle. The finite length filament is a free swimmer, and is driven by an applied torque as well as a counter-torque (of equal strength and opposite direction) that represents a virtual cell body. We use a regularized Stokeslet framework to examine the shape changes of the flexible filament in response to the actuation as well as the swimming performance as a function of the nondimensional Sperm number that characterizes the elastohydrodynamic system. We also show that a modified Sperm number may be defined to characterize the swimming progression within a tube. Finally, we demonstrate that a helical filament whose axis is not aligned with the tube axis can exhibit centering behavior in the narrowest tubes.

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John LaGrone, Ricardo Cortez, Lisa Fauci. 2018-11-16. Elastohydrodynamics of swimming helices: effects of flexibility and confinement. https://doi.org/10.1103/physrevfluids.4.033102

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