Mass-time and space-time fractional partial differential equations of water movement in soils: theoretical framework and application to infiltration
Su, Ninghu (2014) Mass-time and space-time fractional partial differential equations of water movement in soils: theoretical framework and application to infiltration. Journal of Hydrology, 519 (Part B). pp. 1792-1803.
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Abstract
This paper presents mass-time fractional partial differential equations (fPDEs) formulated in a material coordinate for swelling–shrinking soils, and space-time fPDEs formulated in Cartesian coordinates for non-swelling soils. The fPDEs are capable of incorporating mobile and immobile zones or without immobile zones. As an example of the applications, the solutions of the fPDEs are derived and used to construct equations of infiltration. New equations of cumulative infiltration into soils, which are either swelling or nonswelling and with mobile or immobile zones are presented, and published data are used to demonstrate the use of the new equations and derive the parameters. The transport exponent, u, for soils with mobile and immobile zones are given. The transport exponent is the criteria for defining flow patterns: for u < 1, the flow process is sub-diffusion as compared to u = 1 for classic diffusion and u > 1 for super-diffusion.