Two-fluid Electrokinetic Flow in a Circular Microchannel

The two-fluid flow is produced by the combined effects of electroosmotic force in a conducting liquid and pressure gradient force in a non-conducting liquid. The Poisson-Boltzmann and Navier Stokes equations are solved analytically; and the effects of governing parameters are examined. Poiseuille number increases with increasing the parameters involved. In the absence of pressure gradient, the two fluids demonstrate plug-like velocity profiles. The results reveal that the two-fluid electroosmotic pumping flow rate is feasible for a relatively small interface zeta potential; or large wall zeta potential and electrokinetic radius. For particular values of the governing parameters, the flow rate approaches a specific value as the electrokinetic radius tends to infinity. A back flow (a negative value of the resultant flow rate) occurs for sufficiently small values of the wall zeta potential or sufficiently large values of the interface zeta potential (even in the case of pressure-assisted flow). Zero value flow rates may also be attained.