Filter-paper-TBP-PSBMA-BD-u-3.1.txt from Capillary transport in paper porous materials at low saturation levels: normal, fast or superfast?

The problem of capillary transport in fibrous porous materials at low levels of liquid saturation has been addressed. It has been demonstrated that the process of liquid spreading in this type of porous material at low saturation can be described macroscopically by a similar super-fast, nonlinear diffusion model to that which had been previously identified in experiments and simulations in particulate porous media. The macroscopic diffusion model has been underpinned by simulations using a microscopic network model. The theoretical results have been qualitatively compared with available experimental observations within the witness card technique using persistent liquids. The long-term evolution of the wetting spots was found to be truly universal and fully in line with the mathematical model developed. The result has important repercussions for the witness card technique used in field measurements of the dissemination of various low-volatility agents in imposing severe restrictions on collection and measurement times.

针对低液体饱和度（liquid saturation）下纤维多孔介质（fibrous porous materials）内的毛细输运（capillary transport）问题，本研究开展了相关工作。研究表明，低饱和度条件下此类多孔介质内的液体铺展过程，可通过宏观尺度下的超快非线性扩散模型（nonlinear diffusion model）进行描述，该模型与此前在颗粒多孔介质（particulate porous media）的实验与模拟中得到的模型形式一致。该宏观扩散模型的合理性得到了微观网络模型（microscopic network model）模拟结果的支撑。研究采用持久性液体（persistent liquids）结合示踪卡片技术（witness card technique），将理论结果与已有的实验观测结果进行了定性对比。结果发现，润湿斑（wetting spots）的长期演化规律具备真正的普适性，且与所构建的数学模型完全吻合。该研究结果对用于现场测量各类低挥发性试剂扩散的示踪卡片技术具有重要意义，该技术对采样与测量时长存在严格限制。