微管道内两相流数值算法及在电浸润液滴控制中的应用

A numerical method for two-phase flow in micro channels and its application to droplet control by electrowetting on dielectric

叙述了一种模拟电介质电润湿(electrowetting on dielectric,EWOD)下的微液滴的运动的数值方法.采用二阶投影法求解N_S方程和level set函数,并利用零level set函数俘获液滴运动界面,在液体与固体接触的边界上,通过引入动态接触角表征电介质表面润湿性随电势的改变.数值计算基于MAC网格,模拟了2维微管道内与固体壁面接触的变润湿性的两种液体的分界面形状、平板上的微液滴在不同电势作用下处于不同湿润性的形态,以及微管道内改变接触角液滴的运动变形过程等算例.

With the development of micro chemical and medical analysis in MEMS, micro-fluid-control chip becomes more and more popular. Based on discrete droplet control system, chemical and medical analysis is applied in the micro chip lab. The change of voltage between the dielectric layer of the electrode controls the wettability of a droplet on a dielectric solid surface and then makes it possible to create, transport, merge and cut the micro droplets. This paper presents a numerical method to simulate the droplet motion by electrowetting on dielectric （EWOD）. The second-order projection method is carried out to solve N-S equations and level set function. The interface is captured as zero level set. Dynamic contact angle for fluid contacting a solid surface by the electric potential is used to evaluate the wettability of fluid by EWOD. The numerical scheme is based on staggered MAC grid. Numerical simulations are used to capture the interface between two kinds of fluids in micro channels, the shapes of micro droplets resting on the horizontal solid surface under different electric potential and the transportation of a micro droplet in a parallel-plate channel when electrodes are activated.