Abstract
We report three stages for locomotion of a helical swimmer in yield stress fluids. In the first stage, the swimmer must overcome the material’s yield strain to generate rotational motion. However, exceeding the first threshold is not sufficient for locomotion. Only when the viscous forces are sufficiently strong to plastically deform the material to a finite distance away from the swimmer will net locomotion occur. Once locomotion is underway in the third stage, the yield stress retards swimming at small pitch angles. Conversely, at large pitch angles, yield stress dominates the flow by enhancing swimming speed. Flow visualizations reveal a highly localized flow near the swimmer in yield stress fluids.
- Received 27 March 2022
- Accepted 27 January 2023
DOI:https://doi.org/10.1103/PhysRevLett.130.114002
© 2023 American Physical Society
Physics Subject Headings (PhySH)
synopsis
How Microswimmers Push Through Solid-Like Fluids
Published 16 March 2023
If a helical bacteria’s tail propulsion is strong enough to deform the yield-stress fluid ahead of the swimmer, locomotion proceeds.
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