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Viscoelastic fluid rheology suppressed nonuniform conductivity-driven instabilities in electrokinetic flows

Md Mainul Islam, Nicole Miller, Jahir Rayhan, Yuhao Xu, and Xiangchun Xuan*

  • Department of Mechanical Engineering, Clemson University, Clemson, South Carolina 29634, USA

  • *Contact author: xcxuan@clemson.edu
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Phys. Rev. Fluids 11, 113701 – Published 12 November, 2026

DOI: https://doi.org/10.1103/q6pl-vtly

Abstract

Electrokinetic flows involving fluids with nonuniform conductivity can trigger instabilities known as electrokinetic instabilities (EKIs). Prior studies have established the theoretical framework of EKI in Newtonian fluids, where the electric Rayleigh number is identified to govern the onset of instabilities. We propose in this work a theoretical formulation of the electric Rayleigh number for EKI in viscoelastic fluids with conductivity gradients. Our scaling analysis in terms of the Oldroyd-B model predicts that fluid viscoelasticity suppresses EKI through the combined viscous and elastic effects. We also conduct experiments to investigate the effects of fluid viscoelasticity and viscoelasticity gradients on EKI in hyaluronic acid polymer solutions. Our observations verify the theoretical analysis and demonstrate that the presence of viscoelasticity gradients causes a further suppression of EKI with the extent strongly dependent on the direction of rheology gradients. Furthermore, we analyze the perturbation energy, spatiotemporal evolution, and power spectra to understand and compare the EKI dynamics among different fluid combinations.

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Phys. Rev. Fluids 11, 113701– Published 12 November, 2026
  • Received 8 April 2026
  • Accepted 16 October 2026
Article part of CHORUS
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