Instability of electrokinetic flow in a thin fluid layer between two parallel plates with an electrical conductivity gradients
Date Issued
2009
Date
2009
Author(s)
CAI, YING-TING
Abstract
In the microfluidic device, it is the most effective way that the fluid is driven by the electric force is better than pressure. The electrohydrodynamics (EHD) is integrated electricity and the fluid mechanics have the interesting phenomenon. Specially the DC causes the free charge to accumulate when the fluid has conductivity gradient, then occurs unstable convection phenomenon. This kind of stabilization is most often applied to the micromixer. In the present the Micro Electro Mechanical Systems (MEMS) technology is quite important research subjects. This paper mainly considers electroosmotic flow (EOF) of the conductivity gradient distribution to use the linear stability analysis method. The model use dilute binary electrolyte solution between two infinite plates passes over a horizontal electric field. The electric field makes the electric double layer (EDL) in fluid to produce the boundary slip velocity then impetus fluid motion. As a result of the flow field has electric conduction gradient inside to cause the free charge and the electric force are the non-uniform distribution. When the applied electric field continues to increase the critical value then the flow will become unstable. In order to understand that this slip velocity which acts in this system, we calculate separately to have EDL and no two situations. we discover when low conductivity gradient , EDL had the boundary slip velocity indeed to strengthen system unstable. However, at high conductivity gradient when EDL of zeta potential is stronger that system is more stable. This paper use massive value result to explain the important physical mechanism, the achievement will be helpful to the electrohydrodynamic stability a little understanding.
Subjects
electroosmotic flow
stability analysis
horizontal electric field
conductivity gradient
zeta potential
Type
thesis
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