Flow Mixing of two miscible liquids has been characterized experimentally in three different helically coiled reactor configurations of two different lengths in the laminar flow regime at Re = 50…1000. A straight helical coil, a coiled flow inverter, and a new coiled flow reverser have been built, each in a 3-turn and a 6-turn configuration. Laser-induced fluorescence of resorufin has been used to visualize and quantify mixing in cross-sections throughout the reactors. A mixing coefficient is derived from the fluorescence images to allow for a quantitative measure and comparison of the six configurations. It becomes obvious from these experimental results, that an early flow redirection in the helical configuration is beneficial to mixing. The 3-turn reactors achieve nearly the same mixing coefficients as the 6-turn reactors with the double length. This can be explained by the stabilizing effect of the Dean vortices in the helix, which develop during the first two turns. After that, the liquid is trapped inside the vortices and further mixing is inhibited. Accordingly, the coiled flow inverter and coiled flow reverser configurations lead to much higher mixing coefficients than the straight helical coil. The results of these measurements are now used for validation of numerical simulations, which reproduce the geometrical and flow conditions of the experiments. Some exemplary results of these calculations are also shown in this article. Mass fractions of tracer fluid at Re = 500 in the six examined helix configurations.

中文翻译：

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激光诱导荧光在不同螺旋盘绕结构中的混合表征

在 Re = 50…1000 的层流状态中，两种不同长度的三种不同螺旋盘管反应器配置中的两种可混溶液体的流动混合已通过实验表征。一个直螺旋线圈、一个盘绕流逆变器和一个新的盘绕流反向器已经建成，每个都采用 3 匝和 6 匝配置。试卤灵的激光诱导荧光已被用于可视化和量化整个反应器横截面的混合。混合系数源自荧光图像，以允许对六种配置进行定量测量和比较。从这些实验结果可以明显看出，螺旋结构中的早期流动重定向有利于混合。3 匝电抗器与双倍长度的 6 匝电抗器实现了几乎相同的混合系数。这可以通过螺旋中迪安涡旋的稳定作用来解释，它在前两圈中发展。之后，液体被困在漩涡内，进一步混合被抑制。因此，盘绕流逆变器和盘绕流反向器配置导致比直螺旋线圈高得多的混合系数。这些测量结果现在用于验证数值模拟，再现实验的几何和流动条件。本文还显示了这些计算的一些示例性结果。六种螺旋结构中 Re = 500 的示踪流体的质量分数。液体被困在涡流中，进一步混合被抑制。因此，盘绕流逆变器和盘绕流反向器配置导致比直螺旋线圈高得多的混合系数。这些测量结果现在用于验证数值模拟，再现实验的几何和流动条件。本文还显示了这些计算的一些示例性结果。六种螺旋结构中 Re = 500 的示踪流体的质量分数。液体被困在涡流中，进一步混合被抑制。因此，盘绕流逆变器和盘绕流反向器配置导致比直螺旋线圈高得多的混合系数。这些测量结果现在用于验证数值模拟，再现实验的几何和流动条件。本文还显示了这些计算的一些示例性结果。六种螺旋结构中 Re = 500 的示踪流体的质量分数。再现实验的几何和流动条件。本文还显示了这些计算的一些示例性结果。六种螺旋结构中 Re = 500 的示踪流体的质量分数。再现实验的几何和流动条件。本文还显示了这些计算的一些示例性结果。六种螺旋结构中 Re = 500 的示踪流体的质量分数。