PDF(Pubmed)
Abstract：
The two-phase seepage fluid (i.e., air and water) behaviors in undisturbed granite residual soil (U-GRS) have not been comprehensively studied due to a lack of accurate and representative models of its internal pore structure. By leveraging X-ray computed tomography (CT) along with the lattice Boltzmann method (LBM) enhanced by the Shan-Chen model, this study simulates the impact of internal pore characteristics of U-GRS on the water-gas two-phase seepage flow behaviors. Our findings reveal that the fluid demonstrates a preference for larger and straighter channels for seepage, and as seepage progresses, the volume fraction of the water/gas phases exhibits an initial increase/decrease trend, eventually stabilizing. The results show the dependence of two-phase seepage velocity on porosity, while the local seepage velocity is influenced by the distribution and complexity of the pore structure. This emphasizes the need to consider pore distribution and connectivity when studying two-phase flow in undisturbed soil. It is observed that the residual gas phase persists within the pore space, primarily localized at the pore margins and dead spaces. Furthermore, the study identifies that hydrophobic walls repel adjacent fluids, thereby accelerating fluid movement, whereas hydrophilic walls attract fluids, inducing a viscous effect that decelerates fluid flow. Consequently, the two-phase flow rate is found to increase with then-enhanced hydrophobicity. The apex of the water-phase volume fraction is observed under hydrophobic wall conditions, reaching up to 96.40%, with the residual gas-phase constituting 3.60%. The hydrophilic wall retains more residual gas-phase volume fraction than the neutral wall, followed by the hydrophobic wall. Conclusively, the investigations using X-ray CT and LBM demonstrate that the pore structure characteristics and the wettability of the pore walls significantly influence the two-phase seepage process.
摘要：
两相渗流流体(即，由于缺乏准确且具有代表性的内部孔隙结构模型，因此尚未对原状花岗岩残积土（U-GRS）中的空气和水）行为进行全面研究。通过利用X射线计算机断层扫描（CT）以及由Shan-Chen模型增强的晶格玻尔兹曼方法（LBM），本研究模拟了U-GRS内部孔隙特征对水-气两相渗流行为的影响。我们的发现表明，这种流体倾向于更大、更直的渗流通道，随着渗漏的进展，水/气相的体积分数表现出最初的增加/减少趋势，最终稳定下来。结果表明，两相渗流速度对孔隙度的依赖性，而局部渗流速度受孔隙结构分布和复杂性的影响。这强调了在研究原状土壤中的两相流时需要考虑孔隙分布和连通性。观察到残余气相在孔隙空间内持续存在，主要位于孔隙边缘和死区。此外，这项研究发现，疏水壁排斥相邻的流体，从而加速流体运动，而亲水壁吸引液体，诱导减缓流体流动的粘性效应。因此,发现两相流速随着随后增强的疏水性而增加。在疏水壁条件下观察到水相体积分数的顶点，达到96.40%，残余气相占3.60%。亲水壁比中性壁保留更多的残余气相体积分数，其次是疏水壁。最后，X射线CT和LBM的研究表明，孔隙结构特征和孔壁的润湿性显着影响两相渗流过程。
