Effect of macropore tortuosity and morphology on preferential flow through saturated soil: A Lattice Boltzmann study |
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| Institution: | 1. Norwegian University of Life Sciences, P.O. Box 5003, NO-1432, ÅS, Norway;2. University of Southeast Norway, P.O. Box 235, NO-3603, Kongsberg, Norway;3. NIBIO - Norwegian Institute Bioeconomy Research, Division of Environmental and Natural Resources, P.O. Box 115, NO-1431, ÅS, Norway;1. Palacký University Olomouc, Faculty of Science, Department of Algebra and Geometry, 17. listopadu 12, 771 46 Olomouc, Czech Republic;2. Mathematical Institute, Slovak Academy of Sciences, Gre?ákova 6, 040 01 Ko?ice, Slovakia;1. Chongqing Key Laboratory of Mobile Communications Technology, Chongqing University of Posts and Telecommunications, Chongqing, China;2. College of Information Science and Engineering, Northeastern University, Shenyang 110819, China |
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| Abstract: | Unlike micropores where water moves upward or downward based on hydraulic gradient, in macropores, water flows predominantly downward due to the gravity. Therefore, models based on capillary flow are not capable of simulating macropore flow. There are attempts to model the macropore flow using two domains, one for capillary flow and another one for macropores. These models use Richard’s equation for capillary flow and Poiseuille’s law for macropores in which the macropore is approximated to be cylindrical or planar. This study quantifies the magnitudes of the errors induced by this assumption. Influence of macropore shapes and tortuosity was quantified by using a 3D Lattice Boltzmann model, which is capable of simulating fluid flow in micropores as well as macropores of cracked clays. Artificial macropores of constant sectional area and volume, but different shapes were generated in 3D and the influence of macropore shapes, shape related parameters, and tortuosity were systematically investigated. Macropore flow rate decreases with different shapes compared to cylindrical macropores and increase in aspect ratio of sectional shape leads to decrease in macropore flow rate. The maximum effect of bends/turnings along the tortuous macropore was about 25% on overall decrease of flow rate due to tortuosity. However, more detailed study is required on the influence of bends on macropore flow rate. The macropore flow rate reduces by about 70% for tortuosity of 1.41. A prediction equation is verified to predict the flow rate of different shapes and tortuous macropores based on straight cylindrical macropore using aspect ratio and tortuosity factor. |
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| Keywords: | Lattice Boltzmann Fluid flow modeling Macropore flow Tortuosity Hydraulic conductivity Preferential flow |
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