2003 Fiscal Year Final Research Report Summary
Non-uniform water and solute flow in uniform soil media
| Project/Area Number |
13460102
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Irrigation, drainage and rural engineering/Rural planning
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| Research Institution | The University of Tokyo |
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Principal Investigator |
SHIOZAWA Sho The University of Tokyo, Graduate School of Agricultural and Lire Sciences, Associate professor, 大学院・農学生命科学研究科, 助教授 (80134154)
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| Co-Investigator(Kenkyū-buntansha) |
FUJIMAKI Haruyuki University of Tsukuba, Institute of Agricultural and Forest Engineering, lecturer, 農林工学系, 講師 (90323253)
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| Project Period (FY) |
2001 – 2003
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| Keywords | finger flow / Wetting front / Darcy's equation / Soli water flow / infiltration |
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| Research Abstract |
Distinct water-content profiles, having saturated θ-bumps at and immediately behind the wetting front, were observed in narrow columns (9 mm I.D.) of homogeneous air-dry glass beads under downward 1D-infiltration. with applied water fluxes at lower than the saturated hydraulic conductivity. The infiltrating water content profiles and the position of the wetting front as a function of time were also calculated based on Richards' equation using an independently-measured hydraulic conductivity function, K(θ), and water retention characteristic, θ(h), of the drainage process, and by applying a pressure boundary condition, h_<we>, which is almost atmospheric pressure, at the moving wetting front. The good agreement between the calculated profiles and the observed confirms that the dynamic water entry pressure (where θ(h_<we>) is the saturated water content), does exist for air-dried glass beads, although it is in contradiction with the modern theory of unsaturated water flow in porous media. This physical property of the dry media creates an upward negative pressure profile behind the wetting front that would inevitably produce finger flow if the column diameter were larger. At the wetting front, the water content and pressure should be completely discontinuous at the level of pore size, and hence Darcy's equation cannot be applied across the interface between the air-dry and saturated media.
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