Transient electroosmosis in the transverse direction of a fibrous porous medium
Journal
Colloids and Surfaces A: Physicochemical and Engineering Aspects
Journal Volume
481
Pages
577-582
Date Issued
2015
Author(s)
Chiang C.C.
Abstract
The transient electroosmotic response in the porous medium constituted by a homogeneous array of parallel, charged, circular cylindrical fibers filled with an electrolyte solution to the step application of an electric field in the transverse direction is analytically studied. The thickness of the electric double layers surrounding the dielectric cylinders is assumed to be small relative to the radius of the cylinders and the gap width between two adjacent cylinders, but the effect of time-evolving electroosmosis within the thin but finite double layers is incorporated. Through the use of a unit cell model, the transient equation of conservation of the fluid momentum outside the double layer is solved for each cell, in which a single cylinder is enveloped by a coaxial shell of the ionic fluid. Explicit expressions for the transient electroosmotic velocity of the bulk fluid in the Laplace transform as functions of the porosity of the fibrous medium and the electrokinetic radius of the constitutive cylinders are obtained for two different conditions at the virtual boundary of the cell. Our results indicate that the time scale for the growth of electroosmosis is significantly smaller for a fiber matrix with a lower porosity and the electroosmotic velocity increases with a decrease in the double-layer thickness relative to the cylinder radius. ? 2015 Elsevier B.V.
Subjects
Circular cylinder
Electrokinetic flow
Starting electroosmosis
Thin but finite electric double layer
Unit cell model
Type
journal article