To validate the experimental results of Part-1, we conducted a two-phase flow simulation of imbibition of a wetting liquid through 2D microstructures made of ellipses of varying aspect ratios. The flow simulation in the particulate microstructures, characterized by low (ellipse) aspect ratio, produced somewhat even micro-fronts, thus replicating the sharp fronts at the visual (macroscopic) scale observed in Part-1. Whereas simulations in the fibrous microstructures produced highly uneven micro-fronts, suggesting the formation of semi-sharp or diffuse visual fronts. Increasing the porosity from 50% to 70% resulted in solid-phase clustering and led to further increase in the unevenness of micro-fronts, pointing to purely diffuse visual fronts. The evolution of the saturation plots along the flow direction, obtained from area-averaging of fluid-distribution plots, pointed to diffusing of sharp fronts with time. The predictions matched our previous experimental and numerical observations, that is, the particulate media create sharp fronts while the fibrous media create semi-sharp/diffuse fronts.

中文翻译：

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研究工业灯芯中液体自吸过程中的液体前沿。第二部分：DNS 验证

为了验证第 1 部分的实验结果，我们对润湿液通过由不同纵横比制成的 2D 微结构进行的渗吸进行了两相流模拟。以低（椭圆）纵横比为特征的颗粒微结构中的流动模拟产生了稍微均匀的微锋，从而在第 1 部分中观察到的视觉（宏观）尺度上复制了尖锐的锋。而纤维微结构中的模拟产生了高度不均匀的微前沿，表明形成了半锐利或漫反射的视觉前沿。将孔隙率从 50% 增加到 70% 会导致固相聚集，并导致微锋面的不均匀性进一步增加，指向纯粹的漫射视觉锋面。饱和度沿流动方向的演变，从流体分布图的面积平均得到，表明尖锐锋面随时间扩散。这些预测与我们之前的实验和数值观察相匹配，即颗粒介质产生尖锐的前沿，而纤维介质产生半尖锐/扩散的前沿。