Effects of the Grain Size on Dynamic Capillary Pressure and the Modified Green–Ampt Model for Infiltration
Darcy-scale capillary pressure is traditionally assumed to be constant. By contrast, a considerable gap exists between the measured and equilibrium capillary pressures when the same moisture saturation is considered with a high flow rate, and this gap is called the dynamic effect on the capillary pr...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Wiley
2018-01-01
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| Series: | Geofluids |
| Online Access: | http://dx.doi.org/10.1155/2018/8946948 |
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| _version_ | 1832564032655065088 |
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| author | Yi-Zhih Tsai Yu-Tung Liu Yung-Li Wang Liang-Cheng Chang Shao-Yiu Hsu |
| author_facet | Yi-Zhih Tsai Yu-Tung Liu Yung-Li Wang Liang-Cheng Chang Shao-Yiu Hsu |
| author_sort | Yi-Zhih Tsai |
| collection | DOAJ |
| description | Darcy-scale capillary pressure is traditionally assumed to be constant. By contrast, a considerable gap exists between the measured and equilibrium capillary pressures when the same moisture saturation is considered with a high flow rate, and this gap is called the dynamic effect on the capillary pressure. In this study, downward infiltration experiments of sand columns are performed to measure cumulative infiltration and to calculate the wetting front depth and wetting front velocity in sands with different grain sizes. We estimate the equilibrium capillary pressure head or suction head at the wetting front using both the classical Green–Ampt (GAM) and modified Green–Ampt (MGAM) models. The results show that the performance of MGAM in simulating downward infiltration is superior to that of GAM. Moreover, because GAM neglects the dynamic effect, it systematically underestimates the equilibrium suction head in our experiments. We also find that the model parameters α^ and β of MGAM are affected by the grain size of sands and porosity, and the dynamic effect of the capillary pressure increases with decreasing grain size and increasing porosity. |
| format | Article |
| id | doaj-art-5b284e9963ed461f9bf04d4f570f8930 |
| institution | Kabale University |
| issn | 1468-8115 1468-8123 |
| language | English |
| publishDate | 2018-01-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geofluids |
| spelling | doaj-art-5b284e9963ed461f9bf04d4f570f89302025-02-03T01:12:00ZengWileyGeofluids1468-81151468-81232018-01-01201810.1155/2018/89469488946948Effects of the Grain Size on Dynamic Capillary Pressure and the Modified Green–Ampt Model for InfiltrationYi-Zhih Tsai0Yu-Tung Liu1Yung-Li Wang2Liang-Cheng Chang3Shao-Yiu Hsu4Department of Bioenvironmental Systems Engineering, National Taiwan University, Taipei 10617, TaiwanDepartment of Water Resources Engineering and Conservation, Feng Chia University, Taichung 40724, TaiwanDepartment of Bioenvironmental Systems Engineering, National Taiwan University, Taipei 10617, TaiwanDepartment of Civil Engineering, National Chiao Tung University, Hsinchu 30050, TaiwanDepartment of Bioenvironmental Systems Engineering, National Taiwan University, Taipei 10617, TaiwanDarcy-scale capillary pressure is traditionally assumed to be constant. By contrast, a considerable gap exists between the measured and equilibrium capillary pressures when the same moisture saturation is considered with a high flow rate, and this gap is called the dynamic effect on the capillary pressure. In this study, downward infiltration experiments of sand columns are performed to measure cumulative infiltration and to calculate the wetting front depth and wetting front velocity in sands with different grain sizes. We estimate the equilibrium capillary pressure head or suction head at the wetting front using both the classical Green–Ampt (GAM) and modified Green–Ampt (MGAM) models. The results show that the performance of MGAM in simulating downward infiltration is superior to that of GAM. Moreover, because GAM neglects the dynamic effect, it systematically underestimates the equilibrium suction head in our experiments. We also find that the model parameters α^ and β of MGAM are affected by the grain size of sands and porosity, and the dynamic effect of the capillary pressure increases with decreasing grain size and increasing porosity.http://dx.doi.org/10.1155/2018/8946948 |
| spellingShingle | Yi-Zhih Tsai Yu-Tung Liu Yung-Li Wang Liang-Cheng Chang Shao-Yiu Hsu Effects of the Grain Size on Dynamic Capillary Pressure and the Modified Green–Ampt Model for Infiltration Geofluids |
| title | Effects of the Grain Size on Dynamic Capillary Pressure and the Modified Green–Ampt Model for Infiltration |
| title_full | Effects of the Grain Size on Dynamic Capillary Pressure and the Modified Green–Ampt Model for Infiltration |
| title_fullStr | Effects of the Grain Size on Dynamic Capillary Pressure and the Modified Green–Ampt Model for Infiltration |
| title_full_unstemmed | Effects of the Grain Size on Dynamic Capillary Pressure and the Modified Green–Ampt Model for Infiltration |
| title_short | Effects of the Grain Size on Dynamic Capillary Pressure and the Modified Green–Ampt Model for Infiltration |
| title_sort | effects of the grain size on dynamic capillary pressure and the modified green ampt model for infiltration |
| url | http://dx.doi.org/10.1155/2018/8946948 |
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