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Open AccessArticle

Numerical Evaluation of Fractional Vertical Soil Water Flow Equations

1
J. Amorocho Hydraulics Laboratory (JAHL), Department of Civil and Environmental Engineering, University of California, Davis, CA 95616, USA
2
Hydrologic Research Laboratory and JAHL, Department of Civil and Environmental Engineering, University of California, Davis, CA 95616, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Anis Younes
Water 2021, 13(4), 511; https://doi.org/10.3390/w13040511
Received: 30 December 2020 / Revised: 7 February 2021 / Accepted: 12 February 2021 / Published: 16 February 2021
Significant deviations from standard Boltzmann scaling, which corresponds to normal or Fickian diffusion, have been observed in the literature for water movement in porous media. However, as demonstrated by various researchers, the widely used conventional Richards equation cannot mimic anomalous diffusion and ignores the features of natural soils which are heterogeneous. Within this framework, governing equations of transient water flow in porous media in fractional time and multi-dimensional fractional soil space in anisotropic media were recently introduced by the authors by coupling Brooks–Corey constitutive relationships with the fractional continuity and motion equations. In this study, instead of utilizing Brooks–Corey relationships, empirical expressions, obtained by least square fits through hydraulic measurements, were utilized to show the suitability of the proposed fractional approach with other constitutive hydraulic relations in the literature. Next, a finite difference numerical method was proposed to solve the fractional governing equations. The applicability of the proposed fractional governing equations was investigated numerically in comparison to their conventional counterparts. In practice, cumulative infiltration values are observed to deviate from conventional infiltration approximation, or the wetting front through time may not be consistent with the traditional estimates of Richards equation. In such cases, fractional governing equations may be a better alternative for mimicking the physical process as they can capture sub-, super-, and normal-diffusive soil water flow processes during infiltration. View Full-Text
Keywords: fractional governing equations; non-Boltzmann scaling; non-Fickian transport; anomalous diffusion; sub-diffusion; super-diffusion fractional governing equations; non-Boltzmann scaling; non-Fickian transport; anomalous diffusion; sub-diffusion; super-diffusion
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MDPI and ACS Style

Ercan, A.; Kavvas, M.L. Numerical Evaluation of Fractional Vertical Soil Water Flow Equations. Water 2021, 13, 511. https://doi.org/10.3390/w13040511

AMA Style

Ercan A, Kavvas ML. Numerical Evaluation of Fractional Vertical Soil Water Flow Equations. Water. 2021; 13(4):511. https://doi.org/10.3390/w13040511

Chicago/Turabian Style

Ercan, Ali; Kavvas, M. L. 2021. "Numerical Evaluation of Fractional Vertical Soil Water Flow Equations" Water 13, no. 4: 511. https://doi.org/10.3390/w13040511

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