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This content will become publicly available on June 25, 2026

Title: Dynamics of rotating helices in a viscous fluid
We investigate the dynamics of a pair of rigid rotating helices in a viscous fluid, as a model for bacterial flagellar bundle and a prototype of microfluidic pumps. Combining experiments with hydrodynamic modelling, we examine how spacing and phase difference between the two helices affect their torque, flow field and fluid transport capacity at low Reynolds numbers. Hydrodynamic coupling reduces the torque when the helices rotate in phase at constant angular speed, but increases the torque when they rotate out of phase. We identify a critical phase difference, at which the hydrodynamic coupling vanishes despite the close spacing between the helices. A simple model, based on the flow characteristics and positioning of a single helix, is constructed, which quantitatively predicts the torque of the helical pair in both unbounded and confined systems. Finally, we show the influence of spacing and phase difference on the axial flux and the pump efficiency of the helices. Our findings shed light on the function of bacterial flagella and provide design principles for efficient low-Reynolds-number pumps.  more » « less
Award ID(s):
2011401
PAR ID:
10659507
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
Cambridge University Press
Date Published:
Journal Name:
Journal of Fluid Mechanics
Volume:
1013
ISSN:
0022-1120
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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