Hydrodynamic Switching Fronts Polarize Deformable Particle Trains

Linzheng Huang; Hengdi Zhang; Zaicheng Zhang; Zaiyi Shen

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arXiv · 2604.05925

Hydrodynamic Switching Fronts Polarize Deformable Particle Trains

Linzheng Huang·Hengdi Zhang·Zaicheng Zhang·Zaiyi Shen

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Abstract

We show that propagating switching fronts mediate directional state transmission and polarity selection in a passive many-body suspension. In confined trains of slipper-shaped deformable particles in Poiseuille flow, this behavior originates from directionally biased switching between neighboring particles: owing to the fore-aft asymmetry of the slipper, an upstream particle drives switching of its downstream neighbor more effectively than in the reverse direction. A local transition from an opposite-sign pair to a same-sign pair therefore launches a streamwise front that relays the inclination sign from particle to particle. A minimal coarse-grained model with local bistability and directional coupling captures front propagation and arrest. In periodic trains, the fronts coarsen into a uniformly polarized state, whereas in long open trains they arrest and leave persistent polarized domains. Our results point to local bistability and directional coupling as a route to collective polarization in passive many-body systems.

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Linzheng Huang, Hengdi Zhang, Zaicheng Zhang, Zaiyi Shen. 2026-04-07. Hydrodynamic Switching Fronts Polarize Deformable Particle Trains. https://arxiv.org/abs/2604.05925

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