Radial basis function interpolation supplemented lattice Boltzmann method for electroosmotic flows in microchannel.

Abstract

Large gradients of physical variables near the channel walls are characteristic of EOF. The previous numerical simulations of EOFs with the lattice Boltzmann method (LBM) utilize uniform lattice and are not efficient, especially when the electric double layer (EDL) thickness is significantly smaller than the channel height. The efficient LBM simulation of EOF in microchannel calls for a nonuniform mesh which is dense in the EDL region and sparse in the bulk region. In this article, we formulate a radial basis function (RBF)-based interpolation supplemented LBM (ISLBM) to solve the governing equations of EOF, that is, the Poisson, Nernst-Planck, and Navier-Stokes equations, in a nonuniform mesh system. Unlike the conventional ISLBM, the RBF-ISLBM determines the prestreaming distribution functions by using the local RBF-based interpolation over circular supporting regions and is particularly suitable for nonuniform meshes. The RBF-ISLBM is validated by the EOFs in infinitely long and finitely long microchannels. The results show that the RBF-ISLBM possesses excellent robustness and accuracy. Finally, we use the RBF-ISLBM to simulate the EOFs with the hitherto highest electrokinetic parameter, κa, defined by the ratio of channel height a to EDL thickness κ-1 , in LBM simulations of EOF.