Alizadeh A, Zhang L, Wang M
Department of Engineering Mechanics and CNMM, Tsinghua University, Beijing 100084, China.
Department of Engineering Mechanics and CNMM, Tsinghua University, Beijing 100084, China.
J Colloid Interface Sci. 2014 Oct 1;431:50-63. doi: 10.1016/j.jcis.2014.05.070. Epub 2014 Jun 12.
Mixing becomes challenging in microchannels because of the low Reynolds number. This study aims to present a mixing enhancement method for electro-osmotic flows in microchannels using vortices caused by temperature-patterned walls. Since the fluid is non-isothermal, the conventional form of Nernst-Planck equation is modified by adding a new migration term which is dependent on both temperature and internal electric potential gradient. This term results in the so-called thermo-electrochemical migration phenomenon. The coupled Navier-Stokes, Poisson, modified Nernst-Planck, energy and advection-diffusion equations are iteratively solved by multiple lattice Boltzmann methods to obtain the velocity, internal electric potential, ion distribution, temperature and species concentration fields, respectively. To enhance the mixing, three schemes of temperature-patterned walls have been considered with symmetrical or asymmetrical arrangements of blocks with surface charge and temperature. Modeling results show that the asymmetric arrangement scheme is the most efficient scheme and enhances the mixing of species by 39% when the Reynolds number is on the order of 10(-3). Current results may help improve the design of micro-mixers at low Reynolds number.
由于雷诺数较低，在微通道中混合变得具有挑战性。本研究旨在提出一种利用温度图案化壁面产生的涡旋来增强微通道中电渗流混合的方法。由于流体是非等温的，通过添加一个依赖于温度和内部电势梯度的新迁移项，对传统形式的能斯特 - 普朗克方程进行了修正。该项导致了所谓的热电化学迁移现象。通过多种格子玻尔兹曼方法迭代求解耦合的纳维 - 斯托克斯方程、泊松方程、修正的能斯特 - 普朗克方程、能量方程和平流扩散方程，分别得到速度、内部电势、离子分布、温度和物种浓度场。为了增强混合，考虑了三种温度图案化壁面方案，这些方案具有带表面电荷和温度的块体的对称或不对称排列。模拟结果表明，不对称排列方案是最有效的方案，当雷诺数约为10^(-3)时，物种混合增强了39%。目前的结果可能有助于改进低雷诺数下微混合器的设计。
