PIV study of flow through porous structure using refractive index matching
PIV study of flow through porous structure using refractive index matching
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使用折射率匹配对流经多孔结构的 PIV 研究
DOI：
10.1007/s00348-014-1717-5
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发表时间：
2014
影响因子：
2.4
通讯作者：
P. Rudolf von Rohr
中科院分区：
文献类型：
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作者：
R. Häfeli;Marco Altheimer;D. Butscher;P. Rudolf von Rohr
提出了一种碘化钠和碘化锌的水溶液，作为一种流体，它与通过快速成型制造的固体的折射率相匹配。这使得通过多孔结构的单相流的光学测量成为可能。在不同尺寸的多孔结构中进行了有机指数匹配流体（茴香醚）的实验。为了比较不同粘度和不同尺寸的实验，我们采用雷诺相似度推导了标度定律。我们研究的目标量之一是湍流动能耗散率。通过比较各向同性比率，对不同的耗散率估计模型进行了评价。与许多其他研究一样，我们的实验无法将速度场分解到柯尔莫哥洛夫长度尺度，因此，必须考虑到耗散率被低估了。这在不同相对分辨率的实验中是可见的。然而，接近Kolmogorov尺度可以估计可重复的，但被低估的多孔结构内部耗散率的空间分布。在此基础上，采用$$k-\varepsilon$$ k-ε模型对紊流扩散系数进行了估计。将其与相同多孔结构中得到的弥散系数进行比较，我们得出结论，即使在$$Re_p=500$$ Rep=500时，湍流扩散系数也只占轴向传质的一小部分。因此，主要部分归因于泰勒色散。
An aqueous solution of sodium iodide and zinc iodide is proposed as a fluid that matches the refractive index of a solid manufactured by rapid prototyping. This enabled optical measurements in single-phase flow through porous structures. Experiments were also done with an organic index-matching fluid (anisole) in porous structures of different dimensions. To compare experiments with different viscosities and dimensions, we employed Reynolds similarity to deduce the scaling laws. One of the target quantities of our investigation was the dissipation rate of turbulent kinetic energy. Different models for the dissipation rate estimation were evaluated by comparing isotropy ratios. As in many other studies also, our experiments were not capable of resolving the velocity field down to the Kolmogorov length scale, and therefore, the dissipation rate has to be considered as underestimated. This is visible in experiments of different relative resolutions. However, being near the Kolmogorov scale allows estimating a reproducible, yet underestimated spatial distribution of dissipation rate inside the porous structure. Based on these results, the $$k-\varepsilon$$k-ε model was used to estimate the turbulent diffusivity. Comparing it to the dispersion coefficient obtained in the same porous structure, we conclude that even at $$Re_p=500$$Rep=500 the turbulent diffusivity makes up only a small part of mass transfer in axial direction. The main part is therefore attributed to Taylor dispersion.