Rotating electroosmotic flow of two-layer fluids through a microparallel channel

摘要

In this study, rotating electroosmotic flow of two immiscible fluids in a microparallel channel is investigated. The electric double layer (EDL) potential distribution is considered by using linear Poisson-Boltzmann (P-B) equation. Based upon the analytical charge density distribution, an analytical solution of flow velocity can be obtained by solving the modified Navier-Stokes (N-S) equation in the rotating frame. Besides, the equilibrium condition of stress, including shear stress and Maxwell stress, is taken into account as boundary conditions at the interface to analyze the distribution of the two-layer fluids velocity. It is found that, due to the rotational effect of the microchannel, the Coriolis force can generate a (secondary) transverse flow in horizontal direction perpendicular to the mainstream direction and the velocity amplitude of two-layer fluids has a reduced flow along the mainstream direction. In addition, the results indicate that double fluid velocity distribution is strongly influenced by several non-dimensional parameters, such as the dielectric constant ratio epsilon, density ratio rho, viscosity ratio mu of the two layer fluids, rotating angular velocity 6), interface zeta potential difference Delta phi*, interface charge density jump Q, the normalized thickness of two layer Newtonian fluids h*(1), h*(2) and electrokinetic width K-1, K-2. Smaller mu and larger epsilon, Delta phi* lead to larger velocity amplitude for lower fluid (noted as fluid II), but an opposite trend can be found for upper fluid (namely fluid I). The increase of Q or decrease of rho leads to the increases of velocity amplitude for both fluid I and fluid II. Furthermore, interestingly, we observe that the mainstream speed at the interface does not depend on the interface zeta potential difference Delta phi*, the dielectric constant ratio a and electrokinetic width K-2 of fluid II when the depths of h*(1) and h*(2) are identical. (C) 2017 Elsevier Ltd. All rights reserved.