Numerical analysis of electroosmosis in a micro-cavity

The bulk motion of an aqueous solution induced by the application of DC and AC electric fields is studied numerically. The physical model consists of a rectangular micro-cavity filled with dilute, symmetric, binary electrolyte and two completely polarizable cylindrical electrodes. The electric double layer (EDL) model coupled with Navier-Stokes equations governing the electroosmotic flow has been described. The ion-transport in the domain is obtained by solving Poisson-Nernst-Plank equations. We employed IB (immersed boundary) technique for the implementation of boundary conditions and semi-implicit fractional-step method for solving the momentum equations. The Poisson equation for potential distribution is coupled with Nernst-Plank equations for ionic species distribution and solved using CGSTAB iteration solver. Numerical codes are validated using bench-mark problems; driven-cavity-flow and flow over a cylinder. The electric field is almost completely balanced by the accumulation of the counter-ions at the electrodes, at steady state the potential in the most part of domain is zero. The flow field is found predominant in the region near the electrodes.