Microannular electro-osmotic flow with the axisymmetric lattice Boltzmann method

Considering electro-osmotic flow in axisymmetric microducts is of both fundamental interest and practical significance. In this paper, an axisymmetric lattice Boltzmann model which solves the complete nonlinear Poisson-Boltzmann equation is presented to obtain the electric potential distribution in the electrolytes, and another axisymmetric lattice Boltzmann model is employed to solve the velocity field. First, the lattice Boltzmann model is validated by the electric potential distribution in the electrolyte with analytical solutions and finite volume method. Second, velocity distributions in circular tubes at various conditions are discussed. Then, we extend the lattice Boltzmann model for steady and pulsating electro-osmotic flow through annular microducts and the influences of inner to outer radius ratio, inner to outer zeta potential ratio and oscillating frequency are investigated. In addition, a numerical study of electro-osmotic flow in circular and annular microducts considering the non-Newtonian fluid behavior is also conducted for the first time. The results show that the microannular electro-osmotic flow exhibits much difference from the planar flow and the non-Newtonian rheology has significant effect on the flow behavior as well.