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A Simple Approximate Equation to Calculate Diffusivities from One‐Step Outflow Experiments
Author(s) -
Valiantzas J. D.
Publication year - 1989
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1989.03615995005300020005x
Subject(s) - outflow , weighting , simple (philosophy) , nonlinear system , function (biology) , mathematics , soil water , mathematical analysis , statistical physics , physics , geology , soil science , meteorology , philosophy , epistemology , quantum mechanics , evolutionary biology , acoustics , biology
Gardner's approximation for determining soil water diffusivities, D (Θ), from one‐step outflow experiments may deviate significantly from actual D (Θ) values. By the systematic analysis of a weighting function which corrects the Gardner's solution, a new simple and accurate equation is derived. Numerical outflow experiments were performed for a variety of arbitrary D (Θ) functions to demonstrate the validity of the equation. Results indicate that the suggested procedure is applicable even for nonlinear ln D (Θ) functions and is more accurate than other previous methods. The present equation has been applied to analyze one‐step outflow experiments in two soils. Numerical predictions of the outflow volumes are in good agreement with laboratory measurements.