Cellulose foams are representative of many porous engineering solids that can absorb a large quantity of fluid such as water. Experiments are reported to give insight into water rise in cellulose foams and the underlying mechanisms. The water rise characteristic of water height versus time displays a distinct knee on a log-log plot; this knee separates an initial regime where scales as from a subsequent regime where scales as . The rate of water rise below the knee is consistent with the Washburn law of water rise in a single dominant capillary, and the knee in the () curve suggests that the Jurin height of this large capillary has been attained. Water rise in the foam above the knee of the () curve is interpreted as water rise in a population of small capillaries with a wide range of radius that feed off the dominant capillary. A series of critical experiments support this interpretation, including water rise in inclined columns, and water rise from a limited reservoir of water. A simple analytical model is used to provide a physical explanation for the observations. Additionally, X-ray computer tomography is used to deduce the probability density function of the small capillaries. The experimental findings are in support of the hypothesis that water rise in the cellulose foam is driven by capillary action and not by diffusion.

中文翻译：

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水吸入纤维素泡沫中：动力学


纤维素泡沫是许多多孔工程固体的代表，可以吸收大量的液体，例如水。据报道，实验可以深入了解纤维素泡沫中的水分上升及其潜在机制。水位相对时间的水位上升特征在双对数图上显示出明显的拐点；该拐点将初始状态与后续状态分开，其中初始状态的缩放比例为 ，后续状态的缩放比例为 。膝盖以下的水上升速率与单个主导毛细血管中水上升的沃什伯恩定律一致，并且 () 曲线中的膝盖表明该大毛细血管已达到 Jurin 高度。泡沫中水在 () 曲线拐点上方的上升被解释为一群小毛细血管中的水上升，这些小毛细血管具有较大的半径范围，这些毛细血管以主要毛细管为食。一系列关键实验支持了这一解释，包括倾斜柱中的水上升以及有限水库中的水上升。使用简单的分析模型为观察结果提供物理解释。此外，X射线计算机断层扫描用于推导小毛细血管的概率密度函数。实验结果支持这样的假设：纤维素泡沫中的水上升是由毛细管作用而非扩散驱动的。