Flow characterization using PIV measurements in a low aspect ratio randomly packed porous bed
Flow characterization using PIV measurements in a low aspect ratio randomly packed porous bed
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DOI：
10.1007/s00348-013-1497-3
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发表时间：
2013-03
影响因子：
2.4
通讯作者：
Vishal A. Patil;J. Liburdy
中科院分区：
文献类型：
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作者：
Vishal A. Patil;J. Liburdy
低纵横比多孔床（床宽与珠径之比）具有工程应用，如催化反应器、燃烧器和热交换器。床内填料的性质和近壁区域的影响，特别是对于随机填充床，预计会影响速度场，从而影响流的统计特性。平面PIV测量采用折射率匹配在整个随机填充床的离散位置，纵横比为4.67的稳定，低孔雷诺数流量，Repore~ 4。详细的测量不确定度以及方法来确定本地放大率和动态速度范围的确定。使用PIV相关平均法分析了数据，其中最大的速度不确定性来自面外运动。结果表明，对应的几何和速度相关函数在整个床和床的中心线示出了一个随机的速度分布与一个水力直径（或0.38珠直径的基础上，该床的孔隙度）的顺序上的积分长度尺度。当比较中心平面数据与使用整个床的数据时，速度方差增加了1.8倍。结果表明，大的速度方差有助于增加分散估计和方差和积分长度尺度的中心平面数据的基础上，分散系数匹配以及在高纵横比床使用全球数据测量。
Low aspect ratio porous beds (bed width to bead diameter) have engineering applications such as catalytic reactors, combustors and heat exchangers. The nature of the packing within the bed and the influence of the near-wall region especially for randomly packed beds are expected to affect the velocity field and consequently the statistical characteristics of the flow. Planar PIV measurements were taken using refractive index matching at discrete locations throughout a randomly packed bed with aspect ratio of 4.67 for steady, low pore Reynolds number flows,Repore~ 4. Details of the measurement uncertainties as well as methods to determine local magnification and determination of the dynamic velocity range are presented. The data are analyzed using the PIV correlation averaging method with the largest velocity uncertainties arising from out-of-plane motion. Results show the correspondence with the geometric and velocity correlation functions across the bed and that the centerline of the bed shows a random-like distribution of velocity with an integral length scale on the order of one hydraulic diameter (or 0.38 bead diameters based on the porosity for this bed). The velocity variance is shown to increase by a factor of 1.8 when comparing the center plane data versus using data across the entire bed. It is shown that the large velocity variance contributes strongly to increased dispersion estimates and that based on the center plane data of the variance and integral length scales, the dispersion coefficient matches well with that measured in high aspect ratio beds using global data.