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Flow instability and scaling transition near strongly polarised surfaces

Published online by Cambridge University Press:  26 November 2025

Wei Liu ,
Yunfan Huang  and
Moran Wang Open the ORCID record for Moran Wang [Opens in a new window]
Wei Liu
Affiliation:
Department of Engineering Mechanics and ASP, Tsinghua University , Beijing 100084, PR China
Yunfan Huang
Affiliation:
Department of Engineering Mechanics and ASP, Tsinghua University , Beijing 100084, PR China
Moran Wang*
Affiliation:
Department of Engineering Mechanics and ASP, Tsinghua University , Beijing 100084, PR China
*
Corresponding author: Moran Wang, moralwang@jhu.edu
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Abstract

The electrokinetic and unstable behaviour near strongly polarised surfaces cannot be well captured by the canonical asymptotic theory for induced-charge electro-osmosis, and the intrinsic mechanism remains unclear. Using direct numerical simulations and scaling analysis, this paper reveals that, near the strongly polarised surfaces, the strong electric double layer charging induces a strong local electric field, which drives the cations in the electrical double layer to extend to a finite region and form an extended space-charge (ESC) layer. The ESC triggers flow instability near strongly polarised surfaces, causing a transition of the velocity scaling exponent in the electric field dependence from a 2 to a 4/3 power law. The findings and mechanisms pave the way for designs of energy and biomedical systems.

JFM classification

MHD and Electrohydrodynamics: Electrokinetic flows

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Type
JFM Papers
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Journal of Fluid Mechanics , Volume 1024 , 10 December 2025 , A8
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© The Author(s), 2025. Published by Cambridge University Press

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