Experiments on the mixing of two different fluids at low Reynolds number inside helical channels have shown that their curvature and torsion induce secondary flow at the channel cross section, which enhances mixing between liquids. While these channels are mostly of symmetric cross section, e.g., circular and rectangular, recent experiments suggest that helical channels with asymmetric cross sections can enhance mixing even further. There have, however, been few systematic studies on the coupled effect of the asymmetry of a channel cross section and its three-dimensional orientation on the mixing of fluid streams. In this regard, we have examined mixing between three differently dyed streams of cross-linkable silicone material inside triple-helical microchannels; we have also simulated the flow of liquids through such channels using fluent software. Our results show that the length of the interface that separates different liquids at any cross section varies linearly with a nondimensional parameter involving curvature, torsion, axial length, and helix radius of the channel. Moreover, mixing efficiency increases with Péclet number, the exponent of variation being dependent on the Reynolds number of flow.

中文翻译：

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螺旋微通道中的混合分析

在螺旋形通道内以低雷诺数混合两种不同流体的实验表明，它们的曲率和扭曲会在通道横截面上引起二次流动，从而增强了液体之间的混合。尽管这些通道大多具有对称的横截面，例如圆形和矩形，但最近的实验表明，具有非对称横截面的螺旋形通道可以进一步增强混合效果。然而，关于通道横截面的不对称性及其三维取向对流体流混合的耦合作用的系统研究很少。在这方面，我们研究了三螺旋微通道内部三种不同染色的可交联有机硅材料流之间的混合。我们还使用以下方法模拟了液体通过此类通道的流动流利的软件。我们的结果表明，在任何横截面处分离不同液体的界面的长度随涉及通道的曲率，扭转，轴向长度和螺旋半径的无量纲参数线性变化。而且，混合效率随着佩克利数的增加而增加，变化的指数取决于流量的雷诺数。