AC two-immiscible-fluid EOF in a microcapillary

Abstract

Time-periodic aspects of two-liquid flow in a circular microchannel are numerically studied in which electroosmosis and pressure gradient are directly utilized to drive conducting and non-conducting liquids, respectively. The results reveal that hydrodynamic parameters of the two fluids together with the coupling effects between them affect the flow characteristics. Frequency, electrokinetic radius, surface charges at the interface between the two immiscible fluids, viscosity ratio and body force ratio (or equivalently, the ratio of the reference velocities in the pure pressure-and electroosmosis-driven flows) are key parameters which determine primarily important features of the flow. High-frequency flow leads to comparatively small magnitudes of velocity and Poiseuille number; in fact in this case, a finite time is required for momentum to diffuse far into the bulk fluid depending on the angular frequency. In case of higher dynamic viscosity ratio, the flow resistance of the nonconducting fluid is higher, resulting in a steeper velocity gradient at the interface of the conducting liquid. The existence of the interface zeta potential may result in a broader flow field (i.e., higher extrema values). For nonzero body force ratio, a pressure gradient obviously exists in one direction and the periodic flow field is not completely symmetric; hence, a net flow rate in one direction is preferably attained.

Impact of hydrodynamics and rheology of the ion partitioning effect on electrokinetic flow through a soft annulus with a retentive and absorptive wall

“…The EOF of a Newtonian fluid under an AC electric field was investigated numerically by Moghadam 17 through a rectangular microchannel considering different zeta potentials on the inner and outer surfaces. Moghadam and Akbarzadeh 18 studied the various aspects of the time-periodic EOF of a conducting liquid together with a non-conducting liquid within a circular microchannel. Saha et al 19 investigated the steady/unsteady EOF through the nanochannel field with the electrolyte solution being surrounded by an immiscible oil layer under the external AC or DC electric field.…”

Transient Two-Layer Electroosmotic Flow and Heat Transfer of Power-Law Nanofluids in a Microchannel

“…Su et al, presented semi-analytical velocities for two-layer combined electroosmotic and pressure driven flow of Newtonian fluids in a slit microchannel at different electric and hydrodynamic parameters [ 53 ]. Time periodic transport characteristics of two-Newtonian liquid combining electroosmotic and pressure driven flows in a microtube have been studied numerically [ 54 ]. In order to improve transport efficiency and reduce the Joule heating effect in a two-layer pumping system, a magnetic field can be applied in addition to the pressure gradient to form a magneto-hydrodynamic EOF; the corresponding entropy generation analysis has been conducted as well [ 55 , 56 ].…”

Analytical Study of the Electroosmotic Flow of Two Immiscible Power-Law Fluids in a Microchannel

“…A comprehensive analysis on the up to date literature indicates that when two fluids meet at the two-liquid interface, the excess ions exist due to the ions adsorption and thus an EDL forms as a narrow region near the two-liquid interface. As a result, the corresponding electrical shear stress at liquid interface was taken into account in two-liquid model [23]- [29]. In further, the zeta potential difference at two-liquid interface caused by the difference of two fluids properties is incorporated and thus the change in electric potential at the two-liquid interface on the velocity distribution is discussed by treating two fluids as conducting [24] [25].…”