Analysis of errors in finite analytic numerical simulation of flow in unsaturated zone

Numerical methods are often used to solve Richards' equation due to the nonlinearity of the equation. Since Finite Analytic Method(FAM) can better keep the original physical properties of the Richards' equation, it has been widely used in the field of environmental and agricultural engineering in recent years. Based on different principles, there are two kinds of Finite Analytic Methods, namely local linearization FAM and Kirchhoff transform FAM, to simulate moisture movement in unsaturated zone. To explore the differences of numerical performances between the two kinds of FAMs, we have carried out the following researches:first, an existing analytical solution is used to preliminarily validate the two kinds of FAMs. After that, two numerical experiments are conducted to compare the accuracy of two methods. Finally, observed data are used to validate the Kirchhoff transform FAM. Compared to the local linearization FAM, Kirchhoff transform FAM can better control the calculated error and obtain higher accuracy of numerical solutions. Therefore, this study has important significance to improve the theory of FAM, which is applied to simulate unsaturated flow.