Interfacial Electrokinetic Effects on Fluid Flow in Microchannel by a Generalized Lattice Boltzmann Model

A diffuse electric double layer (EDL) in microchannel flow created by the charged surface in contact with an electrolyte solution is characterized by the so-called Debye-Hu¨ckel screening length, which depends on the ionic strength of the solution. Usually, the electric double layer thickness, which is from several nanometers to a few hundreds nanometers, is small in comparison with the microchannel height of a few tens microns. Traditional computational fluid dynamics (CFD) methods for macroscopic hydrodynamic equations have difficulties in such complex fluid dynamics problems involving microscale surface interactions. In this paper, we employ a two-dimensional generalized lattice Boltzmann model in the presence of external forces on a rectangular grid with an arbitrary aspect ratio and nonuniform mesh grids. A modified Poisson-Boltzmann equation is applied to examine the adsorption of ions from solution to a charged surface and obtain the electrostatic potential and ion distribution. An example with electroviscous flow in microchannel is used to validate the prediction ability of the model proposed here. Excellent agreement with experimental results was found.