Abstract In the present study, the moisture distribution on the wetting front during drainage and imbibition in a 2D sand chamber is studied thoroughly. Based on the high-resolution data measured by light transmission method, the moisture distribution is observed and then analyzed quantitatively. During drainage and imbibition, different moisture distributions are observed: (a) during drainage, moisture contents fluctuate in a larger range and fingers can be seen on the wetting front; (b) while during imbibition, moisture contents fluctuate in a smaller range and the wetting front is more regular. The Hurst coefficients are successful in capturing different characteristics of the moisture distribution between drainage and imbibition. During imbibition, the Hurst coefficients are around 0.2 on the wetting front; while during drainage, the Hurst coefficients are around 0.5. As the porosity changes from 0.336 to 0.383, the moisture distribution in the sand chamber does not display obvious change. While as the imbibition rate increases from 5 ml/min to 400 ml/min, the moisture distribution on the wetting front becomes more uniform.

中文翻译：

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二维砂室排水和渗吸过程中润湿锋面水分分布的实验研究

摘要 在本研究中，深入研究了二维砂室排水和吸渗过程中润湿锋面的水分分布。基于透光法测量的高分辨率数据，观察水分分布，然后进行定量分析。在排水和吸收过程中，观察到不同的水分分布：（a）排水过程中，水分含量波动范围较大，在润湿前沿可以看到手指；(b) 在渗吸过程中，水分含量波动范围较小，润湿前沿更规则。Hurst 系数成功地捕捉了排水和渗吸之间水分分布的不同特征。在渗吸过程中，润湿前沿的 Hurst 系数约为 0.2；在排水过程中，Hurst 系数约为 0.5。随着孔隙度从 0.336 变化到 0.383，砂室内的水分分布没有表现出明显的变化。当吸入速率从 5 ml/min 增加到 400 ml/min 时，润湿前沿的水分分布变得更加均匀。