基于高能X射线计算机断层扫描与格子玻尔兹曼方法重构的颗粒聚集体堆积中的流体流动
Fluids flow in granular aggregate packings reconstructed by high-energy X-ray computed tomography and lattice Boltzmann method
AI总结：
本研究利用高能X射线计算机断层扫描和格子玻尔兹曼方法，重构并模拟了不同粒径颗粒聚集体堆积中的流体流动，揭示了孔隙率、壁面效应及孔隙网络参数对渗透率和质量流量的影响。
摘要：
颗粒聚集体中的流体流动特性对于设计缓解城市内涝问题的透水基础设施具有重要意义。在本研究中，使用高能X射线计算机断层扫描（X-CT）设备扫描了五组具有相似平均孔隙率但粒径不同的聚集体堆积。重构了堆积结构。计算了孔隙率，并与通过填充堆积中水的体积和质量测得的孔隙率进行了比较。随后提取并分析了孔隙网络。使用带有BGK（Bhatnagar-Gross-Krook）碰撞模型的格子玻尔兹曼方法（LBM）在堆积的孔隙网络域中进行了流体流动模拟。结果表明，壁面效应对聚集体堆积的孔隙率影响显著，且该影响随聚集体尺寸的增大而增加。此外，泊松定律和幂律可分别用于拟合堆积孔隙网络的配位数和配位体积。而且，聚集体中流体的质量流量受孔隙率影响。在二维切片上，当切片孔隙率增加时，质量流量下降。但对于三维块体，平均质量流量随体积孔隙率的增加而增加。当聚集体尺寸改变时，聚集体堆积的渗透率与平均孔径及配位体积的拟合参数表现出相关的变化趋势。尽管存在合并界面导致流体流动微观参数波动的局限性，但这里的方法和结果可为基于聚集体的材料的数值模拟和优化设计提供知识与见解。
英文摘要：
Properties of fluids flow in granular aggregates are important for the design of pervious infrastructures used to alleviate urban water-logging problems. Here in this work, five groups of aggregates packing with similar average porosities but varying particle sizes were scanned by a high-energy X-ray computed tomography (X-CT) facility. The structures of the packings were reconstructed. Porosities were calculated and compared with those measured by the volume and mass of infilled water in the packing. Then pore networks were extracted and analyzed. Simulations of fluids flow in the packings were performed by using a lattice Boltzmann method (LBM) with BGK (Bhatnagar-Gross-Krook) collision model in the pore-network domain of the packings. Results showed wall effect on the porosity of aggregates packing was significant and the influence increased with the aggregate sizes. In addition, Poisson law and power law can be used to fit the coordination number and coordination volume of the packing's pore network, respectively. Moreover, the mass flow rates of fluids in the aggregates were affected by the porosities. On the two-dimensional slices, the mass flow rate decreased when the slice porosity increased. But for the three-dimensional blocks, the average mass flow rate increased with the volume porosity. And the permeability of the aggregates packing showed correlating change trend with the average pore diameter and fitting parameters of coordination volumes, when the sizes of aggregates changed. Though the limitation of merging interfaces causing fluctuation and discontinuity on micro parameters of fluid flow existed, the methods and results here may provide knowledge and insights for numerical simulations and optimal design of aggregate-based materials.
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