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Fingered flow occurred in the unsaturated soil

非饱和土中发生指状流

基本信息

批准号：
09660263
负责人：
CHO Hiroyuki
金额：
$ 2.11万
依托单位：
Saga University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09660263/
关键词：
unsaturated soil preferential flow wetting front fingered flow glass beads water retention curve water movement solute transportation プリファレンシャルフロー不飽和土フィガリング不飽和透水係数フィンガリング現象 2成層土水分特性

项目摘要

When fingered flow occurs during ponding infiltration in a fine-coarse-textured profile, a thin wet zone forms directly below the textural interface (induction zone). During the onset of wetting front instability, a thin induction zone develops from which many small fingers grow initially. Subsequently, a few of these fingers become dominant; they continue to grow at the expense of the remaining fingers which stagnate. Two possible mechanisms govern this process: (1) the pressure head gradient required to laterally transport water from any location at the soil surface to the nearest finger is such that the water entry value of the dry soil is exceeded at some distance from a finger, thus causing another finger to fully develop at that point, and (2) the flux density strongly amplified wavelength of perturbations of the wetting front or the pressure head. Finger spacing in the former case is determined by the properties of the induction zone, and in the latter case by the flux conducted by an individual finger as well as the water supply rate.In order to investigate flow in the induction zone, and nature and extent of the interaction between the induction zone and the fingers, we performed two-dimensional experiments using a glass-bead porous medium. Pressure heads in the induction zone and the fingers were monitored by microtensiometers. We made small disturbances (notches) at various intervals in the textural interface to trigger finger formation and change the number of fingers occurring at first.

当指状流发生在细-粗纹理剖面的积水入渗过程中时，在纹理界面（诱导区）正下方形成一个薄的湿区。在润湿锋不稳定的发病过程中，一个薄的感应区的发展，许多小手指最初生长。随后，这些手指中的一些变得占主导地位;它们继续增长，而其余的手指则停滞不前。两种可能的机制支配这一过程：（1）将水从土壤表面的任何位置横向输送到最近的指状物所需的压头梯度使得在距指状物一定距离处超过干燥土壤的水进入值，从而导致另一个指状物在该点处完全形成，以及（2）通量密度强烈放大了润湿锋或压头扰动的波长。在前一种情况下的手指间距是由诱导区的属性，并在后一种情况下，由一个单独的手指以及供水率进行的流量，以调查在诱导区的流动，和诱导区和手指之间的相互作用的性质和程度，我们进行了二维实验，使用玻璃珠多孔介质。通过微张力计监测感应区和手指中的压头。我们在纹理界面的不同间隔处进行小扰动（缺口），以触发手指形成并改变最初发生的手指数量。