Hydrology and Earth System Sciences Discussions Experimental Study of Fingered Flow through Initially Dry Sand Hessd
Hydrology and Earth System Sciences Discussions Experimental Study of Fingered Flow through Initially Dry Sand Hessd
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通讯作者：
F. Rezanezhad;H.-J Vogel;K. Roth
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作者：
F. Rezanezhad;H.-J Vogel;K. Roth
发表在《水文学与地球系统科学》上的论文正在接受《水文学与地球系统科学》杂志的开放访问审查。摘要水渗透到粗纹理干燥多孔介质中会变得不稳定，这取决于通过无量纲量（即邦德数和毛细管数）表征的流动条件。不稳定的渗透锋打破流动手指，我们实验研究使用Hele-Shaw细胞。我们进一步开发了一种光trans 5使命的方法来测量流动手指内的水的动态非常详细的高空间和时间分辨率。使用X射线吸收校准该方法，并通过用点扩散函数解卷积来校正测量的光透射率的散射效应。此外，我们应用染料示踪剂来可视化流动指内的速度场。我们分析了在径向生长过程中，手指尖端内、尖端后沿着手指核心以及手指边缘内的水的动态。我们的研究结果证实了以前的研究结果的饱和度过冲在指尖，并揭示了一个饱和度最小值背后的提示作为一个新的功能。手指的发展的特点是逐渐增加的水含量的核心内的手指后面的这个最小值和逐渐扩大的手指到一个准稳定的状态，其演变的时间尺度上的数量级长于手指的演变。在这种状态下，检测到急剧分离成具有快速对流的核心和具有极慢流动的边缘。所有观察到的现象可以一致地解释基于土壤-水特性的滞后行为和由20高流速在指尖处诱导的正压力。
Papers published in Hydrology and Earth System Sciences Discussions are under open-access review for the journal Hydrology and Earth System Sciences Abstract Water infiltration into coarse textured dry porous media becomes instable depending on flow conditions characterized through dimensionless quantities, i.e. the Bond number and the Capillary number. Instable infiltration fronts break into flow fingers which we investigate experimentally using Hele-Shaw cells. We further developed a light trans-5 mission method to measure the dynamics of water within flow fingers in great detail with high spatial and temporal resolution. The method was calibrated using x-ray absorption and the measured light transmission was corrected for scattering effects through deconvolution with a point spread function. Additionally we applied a dye tracer to visualize the velocity field within flow fingers. We analyzed the dynamics of water within 10 the finger tips, along the finger core behind the tip, and within the fringe of the fingers during radial growth. Our results confirm previous findings of saturation overshoot in the finger tips and revealed a saturation minimum behind the tip as a new feature. The finger development was characterized by a gradual increase in water content within the core of the finger behind this minimum and a gradual widening of the fingers to a 15 quasi-stable state which evolves on time scales that are orders of magnitudes longer than those of fingers' evolution. In this state, a sharp separation into a core with fast convective flow and a fringe with exceedingly slow flow was detected. All observed phenomena could by consistently explained based on the hysteretic behavior of the soil-water characteristic and on the positive pressure induced at the finger tip by the 20 high flow velocity.