Wu Chih-Yang, Lai Bing-Hao
Department of Mechanical Engineering, National Cheng Kung University, Tainan 701, Taiwan.
Micromachines (Basel). 2020 Dec 18;11(12):1122. doi: 10.3390/mi11121122.
To enhance fluid mixing, a new approach for inlet flow modification by adding vortex-inducing obstacles (VIOs) in the inlet channels of a T-shaped micromixer is proposed and investigated in this work. We use a commercial computational fluid dynamics code to calculate the pressure and the velocity vectors and, to reduce the numerical diffusion in high-Peclet-number flows, we employ the particle-tracking simulation with an approximation diffusion model to calculate the concentration distribution in the micromixers. The effects of geometric parameters, including the distance between the obstacles and the angle of attack of the obstacles, on the mixing performance of micromixers are studied. From the results, we can observe the following trends: (i) the stretched contact surface between different fluids caused by antisymmetric VIOs happens for the cases with the Reynolds number () greater than or equal to 27 and the enhancement of mixing increases with the increase of Reynolds number gradually, and (ii) the onset of the engulfment flow happens at Re≈125 in the T-shaped mixer with symmetric VIOs or at Re≈140 in the standard planar T-shaped mixer and results in a sudden increase of the degree of mixing. The results indicate that the early initiation of transversal convection by either symmetric or antisymmetric VIOs can enhance fluid mixing at a relatively lower .
为了增强流体混合效果，本文提出并研究了一种在T形微混合器的入口通道中添加诱导涡流障碍物（VIOs）来改变入口流动的新方法。我们使用商业计算流体动力学代码来计算压力和速度矢量，并且为了减少高佩克莱数流动中的数值扩散，我们采用带有近似扩散模型的粒子跟踪模拟来计算微混合器中的浓度分布。研究了包括障碍物之间的距离和障碍物的攻角在内的几何参数对微混合器混合性能的影响。从结果中，我们可以观察到以下趋势：（i）对于雷诺数（）大于或等于27的情况，由反对称VIOs引起的不同流体之间拉伸的接触面出现，并且混合增强随着雷诺数的增加而逐渐增加；（ii）在具有对称VIOs的T形混合器中，吞没流在Re≈125时开始，或者在标准平面T形混合器中在Re≈140时开始，这导致混合程度突然增加。结果表明，对称或反对称VIOs引起的横向对流的早期启动可以在相对较低的条件下增强流体混合。
