Effect of electromigration dispersion and non-Newtonian rheology of a charged solute in a microcapillary

Abstract

The present work is concerned with the electromigration interaction of non-Newtonian fluid in a rectangular micro-capillary under the influence of an external electric field to predict the spatiotemporal dynamics of the solute concentration due to an effective dispersion and migration velocity. The solute concentration is optimized by dispersion and a driving force exploiting the interplay between the sequential ionic distribution and the local electrical conductivity coupled with the characteristics of the fluid. The incompressible Navier–Stokes equation combined with the Poisson equation for the electric field is considered for the flow transport incorporated with the Nernst–Planck equation for the ion transport. The numerical computations are performed for the coupled electro-osmosis/electrophoresis migrated nonlinear equations by a control volume approach for effective dispersion. The analytical observation of electrical conductivity in the case of a planar uniformly charged substrate is found to be varied locally near the sample peak and majorly concentration dependent. The asymptotic analysis for the velocity is made by using the lubrication approximation. The solutal species calculation is made from an area averaged nonlinear advection diffusion equation incorporating the coupled momentum equation. It is observed that the Taylor–Aries dispersion effect is dependent on the flow behavior index of the power law fluid, the flow strength, and the local sample concentration. The study of the time regime and the flow strength dependent instantaneous dispersion has also been conducted.