Numerical simulation of electroosmotic complex flow patterns in a microchannel

Complex electroosmotic flow patterns induced by imposing external electric potentials on an electrolyte fluid contained in a microchannel with uniform and spatially-variable (sinusoidal) surface charges are given in this article. The two-dimensional Navier–Stokes equations coupled with the electric potential equations are solved to generate various flow patterns in the limit of the Stokes flow regime i.e., Re ∼ 0. The coupled system of equations was re-formulated using the vorticity-stream function formulations and have been solved numerically using a second order accurate finite differencing method. Two main groups of cases based on the external potential distributions that assigned to both top and bottom walls are investigated in details. Results have shown that, a simple surface charge distribution can lead to complex electroosmotic flow patterns. For example, different vortical motions such as single and multiple vortices have been generated to show the potential of using electrokinetics phenomena (non-intrusive method) to pattern the flow field in microchannels. This simulation can form a basis to study mixing at the microscale for electrically-driven flows.

► Electroosmotic complex flow patterns induced by imposing electric potential are given.
► Wall with constant and variable external electric potential is used.
► A novel numerical algorithm is used to solve coupled multiphysics problem.