Numerical evaluation of iterative and noniterative methods for the solution of the nonlinear Richards equation

Claudio Paniconi, Alvaro A. Aldama, Eric F. Wood

Research output: Contribution to journalArticle

105 Scopus citations

Abstract

Several noniterative procedures for solving the nonlinear Richards equation are introduced and compared to the conventional Newton and Picard iteration methods. Noniterative strategies for the numerical solution of transient, nonlinear equations arise from explicit or linear time discretizations, or they can be obtained by linearizing an implicit differencing scheme. We present two first order accurate linearization methods, a second order accurate two‐level “implicit factored” scheme, and a second order accurate three‐level “Lees” method. The accuracy and computational efficiency of these four schemes and of the Newton and Picard methods are evaluated for a series of test problems simulating one‐dimensional flow processes in unsaturated porous media. The results indicate that first order accurate schemes are inefficient compared to second order accurate methods; that second order accurate noniterative schemes can be quite competitive with the iterative Newton and Picard methods; and that the Newton scheme is no less efficient than the Picard method, and for strongly nonlinear problems can outperform the Picard scheme. The two second order accurate noniterative schemes appear to be attractive alternatives to the iterative methods, although there are concerns regarding the stability behavior of the three‐level scheme which need to be resolved. We conclude that of the four noniterative strategies presented, the implicit factored scheme is the most promising, and we suggest improved formulations of the method.

Original languageEnglish (US)
Pages (from-to)1147-1163
Number of pages17
JournalWater Resources Research
Volume27
Issue number6
DOIs
StatePublished - Jan 1 1991

All Science Journal Classification (ASJC) codes

  • Water Science and Technology

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