Study Of Microchannl Stratified Liquid Flow And Its Stability With Effects Of Electrical Double Layer

The microflow system of the MEMS technology is applied in fields of environmental monitoring, biochemical analysis, clinic testing and mivroelectronics etc. The flow system with the micron characteristic scale is called microflow. Comparing to the normal scale systems, the interface effects such as the Electrical Double Layer become a main factor to control the behavior of micro scale systems. In this paper, the analytical solution of single phase microflow under the combined effects of electrical double layer and boundary slip and the stratified microflow under the effect of the electrical double layer are established and solved for the first time. Furthermore, the stability of the above mean flows is studied. The main conclusions are as the following:(i) A velocity backflow is raised in the near-wall-area. When the channel height is reduced and the Zeta potential is increased, the velocity is decreased and the backflow is strong. Combining the effects of electrical double layer and boundary slip, the backflow constrains the velocity to slide to the opposite direction and strengthen the restrain effect of electrical double layer so that the backflow is obvious. Combining the effects of electrical double layer, boundary slip and apparent viscosity, the slip velocity is controlled by the couple effects of the electrical double layer and apparent viscosity. The slip velocity is against the flow direction if the effect of electrical double layer is stronger than that of apparent viscosity. The slip velocity is small and an inflection point occurs when the effect of apparent viscosity is stronger than that of electrical double layer.(ii) As the effect of the electrical double layer is becoming strong, the critical Reynolds number is reduced and the critical wave number is increased. The microflow is easily to lose stability. Combining the effects of electrical double layer and boundary slip, the critical Reynolds number is smaller than that of only electrical double layer is considered. The effect of boundary slip reinforces that of electrical double layer. Combining the effects of apparent viscosity and boundary slip, the critical Reynolds number hardly affects by boundary slip and The boundary slip cannot enhance the stability. Combining the effects of electrical double layer, boundary slip and apparent viscosity, the effects of electrical double layer and apparent viscosity decrease the critical Reynolds number corporately. When the effect of electrical double layer is strong, the effect of boundary slip can further weaken the stability of system. When the effect of apparent viscosity is strong, the effect of boundary slip is weakened and the inflection point decreases the critical Reynolds number.(iii) With respect to the stratified flow consisting of deionized solution and ion solution, the stronger the electrical double layer effect is, the bigger the restrain force and the stronger the backflow on the side of the ion solution are. With respect to the stratified flow consisting of two different ion solutions, the backflow on both sides restrain the flow. The backflow on the side of flow with big viscosity effect is stronger than that with the small viscosity effect. The flow of upper layer is restrained more when the Zeta potential ratio is big.(v) With respect to the stratified flow consisting of the deionized solution and ion solution, the critical Reynolds number is reduced when the Zeta potential of the ion solution increases. With respect to the stratified flow consisting of two different ion solutions, the Zeta potential also makes the stability of flow decreased. Comparing with the above two conditions, stratified ion solutions flow is more unstable. When the viscosity ratio is bigger than 1, the closer the interface to the upper wall, the more stable the flow is. The bigger the viscosity ratio is, the more unstable the flow is. The stability of flow is increased by the conductivity of solution.