Elastohydrodynamics of swimming helices: effects of flexibility and confinement

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.

References in corpus (8)

• Bacterial hydrodynamics
• Theory of swimming filaments in viscoelastic media
• Low-Reynolds number swimming in a capillary tube
• Propulsion and instability of a flexible helical rod rotating in a viscous fluid
• Enhanced motility of a microswimmer in rigid and elastic confinement
• Rotational dynamics of a soft filament: wrapping transition and propulsive forces
• Propulsion by a Helical Flagellum in a Capillary Tube
• Deformation and shape of flexible, microscale helices in viscous flow

Cited by in corpus (7)

• Flexible filaments buckle into helicoidal shapes in strong compressional flows
• Swimming in Complex Fluids
• Jeffery's orbits and microswimmers in flows: A theoretical review
• Complex dynamics of long, flexible fibers in shear
• A remeshed vortex method for mixed rigid/soft body fluid--structure interaction
• The regularized Stokeslets method applied to the three-sphere swimmer model
• Undulatory swimming in suspensions and networks of flexible filaments