Resistance Effect of Electric Double Layer on Liquid Flow in Microchannel
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摘要: 采用数值方法求解双电层的Poisson-Boltzmann方程和液体运动的Navier-Stokes方程，研究微通道双电层对压强梯度液体流动的阻力效应． 量纲分析表明，双电层阻力大小可以用一个无量纲的电阻力数表示．它与液体的介电系数、固体表面的zeta电位平方成正比，与液体的动力粘性系数、电导率以及微通道的宽度平方成反比．在计算流动诱导的流动电位势和电阻力时，提出电流密度平衡条件，可以消除传统电流平衡条件导致的固壁附近产生局部回流的不合理物理现象．还给出不同电阻力数的微通道流量、流量损失率、速度剖面的数值结果，合理解释了双电层对微通道液体流动的阻力效应．Abstract: Poisson-Boltzmann equation for electric double layer and Navier-Stokes equation for liquid flows to investigate resistance effect of electric double layer on liquid flow in microchannel were nu merically solved. The dimension analysis indicates that the resistance effect of electric double layer can be estimated by an electric resistance number, which is proportional to the square of the liquid dielec tric constant and the solid surface zeta potential, and inverse-proportional to the liquid dynamic vis cosity, electric conductivity and the square of the channel width. An electric current density balancing (ECDB) condition was proposed to evaluate the flow-induced streaming potential and electric resis tance, instead of conventional electric current balancing(ECB) condition which may induce spurious local backflow in neighborhood of solid wall of the microchannel. The numerical results of the flow rate loss ratio and velocity profile are also given to demonstrate the resistance effect of electric double layer in microchannel.
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Key words:
- microchannel /
- electric double layer /
- electric resistance number
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