Two-layer combined electroosmotic and pressure-driven flow of power-law fluids in a circular microcapillary

Abstract

A two-layer combined electroosmotic and pressure driven flow of power-law fluids in a circular microchannel occurs under the coupling effect of electric double layers near the solid interface and near the two-liquid interface, the applied electric field and pressure gradient. When the inner and peripheral fluids are both characterized by power-law model, the mechanism of dragging power-law fluid and the mechanism of using power-law fluid as driving force in a circular microchannel are firstly discussed, thereby the quantitative control of two-liquid system is allowed. Using Poisson-Boltzmann equation and modified Cauthy momentum equation in cylindrical coordinate, the model for two-layer electric potential and velocity distributions are proposed. The two-layer combined electroosmotic and pressure driven flow under the interaction of power-law constitutive relation and wall effect of circular microchannel is examined by evaluating the velocities and flow rates as functions of viscosities and electroosmotic characters of two fluids. The velocity and flow rate of inner flow depend on the viscosities and electroosmotic characters of both inner and peripheral fluids. In contrast, the parameters involved with inner fluid show little influence on the peripheral flow, and thus the velocity and flow rate of peripheral flow can be considered as functions of the viscosity and electroosmotic characters of peripheral fluid. When the inner fluid is nonconducting, the two-layer flow exhibits as a single-layer flow.