Unstable infiltration experiments in dry porous media

Prediction of infiltration in porous media is challenged by finger formation and unstable displacement of the wetting front. We present a systematic experimental study on the effect of packings and infiltration rates on unstable flow into initially dry porous media. We conducted small two- and three-dimensional experiments where water contents were measured with neutron radiography and larger two-dimensional experiments, which we evaluated by obtaining commonly used finger properties such as width and velocity from image analysis. Our results from experiments in macroscopically homogeneous packings were tested for correspondence with theoretical finger property predictions and are in good agreement. For the smaller experiments, water content profiles including “overshoots” at the finger tips as well as finger properties depending on the packing matched well results reported in the literature. For all homogeneous experiments, we found a strong dependence of finger properties on porosity....

多孔介质（porous media）内渗流的预测受指流形成与湿润锋面（wetting front）不稳定运移的制约。本研究针对填充结构与渗流速率对初始干燥多孔介质内不稳定渗流的影响开展系统性实验研究。本研究开展了小型二维与三维渗流实验，采用中子射线照相术（neutron radiography）测量含水率；同时开展了大型二维渗流实验，通过图像分析提取指流宽度、流速等常用指流特征参数完成实验评估。针对宏观均匀填充介质的实验结果，我们与理论指流特征参数预测结果进行了一致性验证，二者吻合度良好。针对小型实验，指流锋端存在含水率分布剖面超调现象，且依赖于填充结构的指流特征参数与已有文献报道结果吻合度较高。所有均匀填充介质实验均表明，指流特征参数与孔隙率存在显著的依赖关系……