Fluid flow characterisation in randomly packed microscale porous beds with different sphere sizes using micro-particle image velocimetry
Fluid flow characterisation in randomly packed microscale porous beds with different sphere sizes using micro-particle image velocimetry
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DOI：
10.1016/j.expthermflusci.2020.110136
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发表时间：
2020-10
影响因子：
3.2
通讯作者：
Xianke Lu;Yuyuan Zhao;D. Dennis
中科院分区：
文献类型：
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作者：
Xianke Lu;Yuyuan Zhao;D. Dennis
为了更好地了解不同尺寸球体随机堆积微孔床内不同流态下的流体流动特性，采用压降和μ-PIV进行了实验研究。用平均直径分别为170μm、430μm和710μm的玻璃微珠在两块载玻片之间进行微烧，制得3个烧结玻璃样品，形成夹层结构的样品。通过压降测量，在每个烧结玻璃样品中识别出四种不同的区域，即前Darcy、Darcy、Forchheimer和湍流。渗透率随玻璃球尺寸的增大而增大，各流区边界对应的雷诺数也随之增大。结果表明，对于给定的Re，直径为170μm的样品的压降可比直径为710μm的样品的压降大10倍。四种不同的孔几何形状被确定为μ-PIV测量区域的焦点，这些区域是在压降测量中确定的所有流型的范围内重新获取的。对于直径为170μm和430μm的样品，各流型的无因次时均速度分布相似，而对于直径为710μm的样品，无因次时均速度分布变化很大。一般情况下，在多孔介质中流道的速度分布是接近抛物线的，特别是在Darcy和Forchheimer区域，但在湍流区域，观察到了惯性效应，如局域射流。对速度分布的详细观测和统计分析突出了它们对局部几何形状的强烈依赖性，高度局部化的流动区域显然处于与主体流动不同的流型中。然而，整个测量区的波动的全球平均值确实与压降测量结果吻合得很好。
An experimental study using pressure-drop and μ-PIV measurements was undertaken to better understand the fluid flow characteristics in different flow regimes within randomly packed microscale porous beds with different sized spheres. Three sintered glass samples were made with glass spheres having a mean diameter of 170 μ m, 430 μ m and 710 μ m by slightly sintering them between two glass slides, forming a sample with a sandwich structure. Four different regimes, pre-Darcy, Darcy, Forchheimer and turbulent were identified in each sintered glass sample using the pressure-drop measurements. The permeability increases with glass sphere size and so does the Reynolds number corresponding to each flow regime boundary. It was found that for a given Re, the pressure drop in the sample with 170 μ m diameter spheres can be ten times higher than the pressure drop in the sample with 710 μ m diameter spheres. Four different pore geometries were identified to be the focus of the measurement zones of the μ-PIV, which were taken across a range of Re spanning all the flow regimes identified in the pressure-drop measurements. The non-dimensional time-averaged velocity distribution was found to be similar in each flow regime for the samples with 170 μ m and 430 μ m diameter spheres, whereas it changed dramatically for the sample with 710 μ m diameter spheres. In general the velocity profiles through the channels within the porous media were found to be near-parabolic, especially in the Darcy and Forchheimer regimes, but in the turbulent regime inertial effects such as localised jets were observed. Detailed observational and statistical analysis of the velocity distributions highlights their very strong dependency on the local geometry with highly localised regions of flow apparently in a different flow regime to that of the bulk flow. However, the global average of the fluctuations throughout the measurement zone does align well with the pressure drop measurements.