Lagrangian dynamics unveil polymer conformation in viscoelastic flows
Abstract
The complex flow behavior of viscoelastic fluids emerges from a feedback between fluid stress and the out-of-equilibrium conformational dynamics of their constituent polymer chains. While constitutive models can predict flow and stress fields in simple geometries, a fundamental understanding of the mechanisms regulating viscoelastic flows with mixed kinematics and non-trivial polymer dynamics remains elusive. Quantifying the history-dependent conformation of polymer chains in flow is essential to resolve these complex systems. To address this knowledge gap, we employ direct Lagrangian tracking of individual DNA molecules to reveal their conformational dynamics in microfluidic viscoelastic flows for different polymer contour lengths and concentrations. Comparing the measured molecular extension and orientation reveals discrepancies with canonical constitutive models, which do not fully capture the transient dynamics. Our measurements show a distinct anisotropy in polymer relaxation and shape, which couple the polymer's rotation and extension through hydrodynamic drag, regulating their Lagrangian mechanics. These findings emphasize the importance of Lagrangian polymer history and the need to account for non-trivial intra-molecular mechanics to improve constitutive descriptions of viscoelastic flows.
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BibTeX
@misc{thorens2026lagrangian,
title = {{Lagrangian dynamics unveil polymer conformation in viscoelastic flows}},
author = {Louison Thorens and Gabriel Juarez and Jeffrey S. Guasto and Paulo E. Arratia},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.04538},
eprint = {2609.04538},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.04538},
}
RIS
TY - UNPB
TI - Lagrangian dynamics unveil polymer conformation in viscoelastic flows
AU - Louison Thorens
AU - Gabriel Juarez
AU - Jeffrey S. Guasto
AU - Paulo E. Arratia
PY - 2026
DA - 2026/09/03
PB - arXiv
DO - 10.48550/arxiv.2609.04538
UR - https://arxiv.org/abs/2609.04538
AB - The complex flow behavior of viscoelastic fluids emerges from a feedback between fluid stress and the out-of-equilibrium conformational dynamics of their constituent polymer chains. While constitutive models can predict flow and stress fields in simple geometries, a fundamental understanding of the mechanisms regulating viscoelastic flows with mixed kinematics and non-trivial polymer dynamics remains elusive. Quantifying the history-dependent conformation of polymer chains in flow is essential to resolve these complex systems. To address this knowledge gap, we employ direct Lagrangian tracking of individual DNA molecules to reveal their conformational dynamics in microfluidic viscoelastic flows for different polymer contour lengths and concentrations. Comparing the measured molecular extension and orientation reveals discrepancies with canonical constitutive models, which do not fully capture the transient dynamics. Our measurements show a distinct anisotropy in polymer relaxation and shape, which couple the polymer's rotation and extension through hydrodynamic drag, regulating their Lagrangian mechanics. These findings emphasize the importance of Lagrangian polymer history and the need to account for non-trivial intra-molecular mechanics to improve constitutive descriptions of viscoelastic flows.
ER -