Hydrodynamic cascade drives tumbling in sheared colloidal rod suspensions
Abstract
Modeling the dynamics of colloidal rods remains a central challenge in soft-matter physics due to the anisotropic and long-ranged nature of their interactions. Hydrodynamic interactions in rods suspensions are often assumed to be screened or too week to play any role in semi-dilute regimes, yet we find here these assumptions to break down at shear rates and concentrations that are often attained in experiments. Using particle-based simulations and scaling analysis, we uncover a cascade of tumbling events driven by hydrodynamic coupling among neighboring rods. This collective dynamics disrupts flow alignment and leads to a pronounced increase in viscosity and normal stress differences, in qualitative agreement with recent experiments. The discovery of this hydrodynamically-promoted cascade effect calls for a revision of existing constitutive models for colloidal rods and highlights hydrodynamic coupling as a key mechanism governing collective dynamics in highly anisotropic suspensions.
Cite
@article{arxiv.2605.16723,
title = {Hydrodynamic cascade drives tumbling in sheared colloidal rod suspensions},
author = {Lucas H. P. Cunha and Paul F. Salipante and Peter D. Olmsted and Steven D. Hudson},
journal= {arXiv preprint arXiv:2605.16723},
year = {2026}
}