Author(s)

Luca Bergamaschi & Mario Putti

Abstract

In this work, we present a two-dimensional mixed-hybrid finite element model of variably saturated flow on unstructured triangular meshes. Veloc- ities are approximated using lowest order Raviart-Thomas (RTo) elements with piecewise constant pressure. The resulting nonlinear systems of alge- braic equations are solved using Picard or Newton iterations. Theroretical superconvergence properties of the RTo approach are ex- perimented on analytical sample problems. It is shown that second order convergence on the pressure head and velocity fields can be obtained at particular points of the triangulation also on nonuniform meshes. Simulations on a realistic sample test show that the Newton approach achieves fast convergence if a good initial guess is provided by either the Picard

Keywords