The impact of water droplets on thin porous layers of glass beads held vertically between glass plates was photographed to observe simultaneous spreading and infiltrating of the liquid into the porous medium. Glass beads with diameters of either 100 µm or 500 µm were tested and micro-computed tomography was used to measure the porosities of the layers. The water drop diameter was kept constant at 2 mm while the impact velocity was varied from 0.06, to 1.9 m/s. High-speed videos of the advance of water into the porous structure were studied with image analysis software and the volume flow rate of liquid calculated. Increasing droplet impact velocity decreases droplet infiltration time because higher droplet inertia drives more liquid into the porous material and a larger droplet spreading diameter increases the area in contact with the substrate. Too high of an impact velocity results in droplet cleaving where a portion of the drop remains on the upper surface. A simple model is proposed to determine when inertia driven infiltration will be significant. Once droplet inertia is dissipated capillary forces draw liquid into the substrate and analytical models are compared to predict the rate of capillary driven flow.

中文翻译：

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影响液滴渗入多孔基材

拍摄水滴对垂直固定在玻璃板之间的玻璃珠的多孔薄层的影响，以观察液体同时扩散和渗透到多孔介质中。测试了直径为 100 µm 或 500 µm 的玻璃珠，并使用微型计算机断层扫描来测量层的孔隙率。水滴直径保持恒定在 2 毫米，而冲击速度从 0.06 变化到 1.9 m/s。用图像分析软件研究了水进入多孔结构的高速视频，并计算了液体的体积流量。增加液滴撞击速度会减少液滴渗透时间，因为更高的液滴惯性驱使更多的液体进入多孔材料，并且更大的液滴扩散直径增加了与基材的接触面积。冲击速度太高会导致液滴分裂，其中一部分液滴保留在上表面。提出了一个简单的模型来确定惯性驱动的渗透何时会显着。一旦液滴惯性消散，毛细管力将液体吸入基板，并比较分析模型以预测毛细管驱动流动的速率。