An implicit-explicit solution method for electro-osmotic flow through three-dimensional micro-channels

This paper presents a comprehensive finite-element modelling approach to electro-osmotic flows on unstructured meshes. The non-linear equation governing the electric potential is solved using an iterative algorithm. The employed algorithm is based on a preconditioned GMRES scheme. The linear Laplace equation governing the external electric potential is solved using a standard pre-conditioned conjugate gradient solver. The coupled fluid dynamics equations are solved using a fractional step-based, fully explicit, artificial compressibility scheme. This combination of an implicit approach to the electric potential equations and an explicit discretization to the Navier–Stokes equations is one of the best ways of solving the coupled equations in a memory-efficient manner. The local time-stepping approach used in the solution of the fluid flow equations accelerates the solution to a steady state faster than by using a global time-stepping approach. The fully explicit form and the fractional stages of the fluid dynamics equations make the system memory efficient and free of pressure instability. In addition to these advantages, the proposed method is suitable for use on both structured and unstructured meshes with a highly non-uniform distribution of element sizes. The accuracy of the proposed procedure is demonstrated by solving a basic micro-channel flow problem and comparing the results against an analytical solution. The comparisons show excellent agreement between the numerical and analytical data. In addition to the benchmark solution, we have also presented results for flow through a fully three-dimensional rectangular channel to further demonstrate the application of the presented method. Copyright q 2007 John Wiley & Sons, Ltd.