Empirical formulas for dynamic effective suction head in the modified green-ampt model
Journal
Journal of Hydrology
Journal Volume
642
Start Page
131820
Date Issued
2024-10
Author(s)
Abstract
The Green-Ampt model, which is a widely used infiltration model, assumes a constant effective suction head during infiltration; however, the capillary pressure is dynamic and related to the saturation rate. One factor affecting the dynamic suction head is the dynamic contact angle, which is parameterized using different formulas. Previous studies applied a power-law formula to parameterize the effective suction head, which substantially improved the ability to describe the velocity-dependent suction head. However, other dynamic contact angle formulas have not been tested. In this study, we performed a series of 1-D downward infiltration experiments with 60-cm sand columns and constructed modified Green-Ampt models (MGAMs) based on four formulas of dynamic contact angle (power-law, Jiang’s law, Hoffman’s law, and Cox-Voinov law) and a linear approximation. These modified Green-Ampt models were named MGAM-PW, MGAM-Jiang, MGAM-Hoff, MGAM-CV, and MGAM-LN. After parameter optimization, all modified Green-Ampt models resulted in similar root-mean-square errors, which were lower than those of the classical Green-Ampt model. The modified Green-Ampt models yielded similar values for the equilibrium suction head, which were larger than those of the classical Green-Ampt model. Among the modified Green-Ampt models, MGAM-CV has an intrinsic limitation in the range of parameter values. MGAM-Hoff typically requires more fitting parameters than do the other methods. MGAM-LN can be solved more efficiently than other modified Green-Ampt models because of its analytical solution and small number of fitting parameters. We demonstrated that the data length and slight time delay of the measurement affected optimization of the equilibrium suction head. Moreover, the relationship between the capillary pressure and saturation rate based on MGAM-PW was similar to the findings in the literature.
Subjects
Green-Ampt model
Dynamic suction head
Dynamic contact angle
Modified Green-Ampt models
SDGs
Publisher
Elsevier
Type
journal article