An adaptive time discretization of the classical and the dual porosity model of Richards’ equation

This paper presents a numerical solution to the equations describing Darcian flow in a variably saturated porous medium—a classical Richards’ equation model Richards (1931) [1] and an extension of it that approximates the flow in media with preferential paths—a dual porosity model Gerke and van Genuchten (1993) [8]. A numerical solver to this problem, the DRUtES computer program, was developed and released during our investigation. A new technique which maintains an adaptive time step, defined here as the Retention Curve Zone Approach, was constructed and tested. The aim was to limit the error of a linear approximation to the time derivative part. Finally, parameter identification was performed in order to compare the behavior of the dual porosity model with data obtained from a non-homogenized fracture and matrix flow simulation experiment.