Electro-magneto-kinetic thermo-fluid-structure interactions of viscoelastic electrolytes through soft micro-confinements.

Abstract

A coupled electro-magneto-hydrodynamic (EMHD) framework for a viscoelastic electrolyte (of Phan-Thien-Tanner (PTT) fluid rheology) flowing through a compliant micro-confinement with linearly elastic walls is developed. The flow is driven by a combination of an imposed pressure gradient and externally applied electric and magnetic fields. Closed-form perturbation solutions are obtained for the velocity, pressure, wall deformation, and temperature. Fluid-structure interactions (FSI) are examined against four parameters: Debye-Huckel parameter (<i></i>), Weissenberg number (Wi), Hartmann number (Ha), and electrical Reynolds number (<i>S</i>). We show that favourable pressure gradients drive wall contractions towards a converging channel, while adverse gradients cause wall expansion to a diverging geometry. Observations also show that <i></i> reduces the pressure requirement through electroosmotic pumping; Wi induces shear-thinning that flattens velocity profiles; Ha has a dual effect - assistive at low Ha and resistive at higher Ha due to Lorentz drag; and <i>S</i> is consistently assistive, lowering the required pressure drop and enhancing near-wall transport. Thermal behaviour is characterized using three parameters-the Biot number (Bi), the Peclet number (Pe), and the wall-to-fluid conductivity ratio (<i>k</i>_r): higher Bi improves cooling <i>via</i> wall-environment exchange, larger Pe increases axial thermal advection and raises fluid temperature, and higher <i>k</i>_r facilitates heat removal and limits thermal buildup. Collectively, the insights provide a systematic approach for regulating hydrodynamic resistance and thermal loading in deformable EMHD microsystems, with potential applications in bio-lab-on-chip technologies and microscale thermal management platforms.