Effective flow and transport properties of heterogeneous unsaturated soils
| Autor: | Rachid Ababou, Veena S. Soraganvi, M. S. Mohan Kumar |
|---|---|
| Přispěvatelé: | Basaveshwar Engineering College (INDIA), Institut de mécanique des fluides de Toulouse (IMFT), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées, Indian Institute of Science, Centre National de la Recherche Scientifique - CNRS (FRANCE), Indian Institute of Science - IISC (INDIA), Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE), Université Toulouse III - Paul Sabatier - UT3 (FRANCE), Institut de Mécanique des Fluides de Toulouse - IMFT (Toulouse, France) |
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Length scale
Solute concentration Stratified media Unsaturated macro-dispersion 010504 meteorology & atmospheric sciences Harmonic mean Mécanique des fluides 0208 environmental biotechnology Spatial moments 02 engineering and technology Stochastic unsaturated flow and transport Suction 01 natural sciences Physics::Geophysics Upscaling [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph] [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology Unsaturated macro-dispersion Hydrologie 0105 earth and related environmental sciences Water Science and Technology Physics Random field Advection Mathematical analysis Isotropy Spatially correlated random fields Randomly heterogeneous soils Richards equation 020801 environmental engineering Effective unsaturated conductivity Stratified media Anisotropy Soil moisture Geometric mean Arithmetic mean |
| Zdroj: | Advances in Water Resources Advances in Water Resources, Elsevier, 2020, 143, pp.103655. ⟨10.1016/j.advwatres.2020.103655⟩ |
| ISSN: | 0309-1708 |
| DOI: | 10.1016/j.advwatres.2020.103655⟩ |
| Popis: | International audience; The heterogeneity of field scale soils poses a challenge to predictive large scale flow and transport modeling. The theory of effective macroscale parameters holds good and is applicable in dealing with such problems. But the va- lidity of the analytic stochastic solutions obtained for randomly heterogeneous soils is debatable, as the test cases under which they are validated are of limited scope due to linearization and perturbation approximations. In this study, samples of heterogeneous soils are generated using sets of spatially correlated random field parameters that are either geometrically isotropic, or else, geometrically anisotropic with either horizontal or vertical stratifi- cation (perfect or imperfect). Several combinations of ratios of correlation length and capillary dispersion lengths are considered. Numerical simulations of unsaturated flow are performed on each randomly heterogeneous soil sample. The principal components ̂K ii (Ψ) of the macroscale effective unsaturated conductivity are then obtained as a function of the mean suction Ψof the sample. They are compared to stochastic spectral perturbation theory, and to a probabilistic semi-empirical Power Average Model (PAM). They are also compared with arithmetic, geo- metric and harmonic mean conductivity-suction curves. The numerically upscaled principal conductivity curves match quite well the PAM, better than the classical means (Arithmetic, Geometric, Harmonic), and also some- what better than the curves obtained from stochastic spectral perturbation theory. It is observed that the upscaled principal components K ii ( ????), obtained numerically and with the PAM along directions “i ”orthogonal/parallel to perfect stratification coincide with the harmonic/arithmetic mean curves at low suctions (i.e., near saturation), but deviate from it and come closer to the geometric mean at higher suctions. The PAM appears suitable for generation of approximate upscaled conductivity curves, e.g., for obtaining the mesh-scale or block-scale con- ductivity curves in large scale simulation codes. Transient solute transport simulations are then performed on the detailed random velocity fields obtained from the steady state simulations of unsaturated flow in the randomly heterogeneous soil samples. Snapshots of solute concentration C(x,z,t) are taken at different times. The temporal evolution of spatial moments of concentration is analyzed in order to characterize the macroscale advection and dispersion of the unsaturated concentration plume, and in particular, its macro-dispersion coefficient (D) and dis- persivity length scale (A). For the synthetic soil samples considered in this study, the macro-dispersive spreading of the solute is stronger for flow parallel to vertical stratification, compared to flow perpendicular to horizontal stratification, and also, compared to flow in statistically isotropic non-stratified soil. |
| Databáze: | OpenAIRE |
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