NUMERICAL ANALYSIS OF A NONLINEARLY STABLE AND POSITIVE CONTROL VOLUME FINITE ELEMENT SCHEME FOR RICHARDS EQUATION WITH ANISOTROPY

We extend the nonlinear Control Volume Finite Element scheme of [C. Cances and C. Guichard, Math. Comput. 85 (2016) 549-580]. to the discretization of Richards equation. This scheme ensures the preservation of the physical bounds without any restriction on the mesh and on the anisotropy tensor. Moreover, it does not require the introduction of the so-called Kirchhoff transform in its definition. It also provides a control on the capillary energy. Based on this nonlinear stability property, we show that the scheme converges towards the unique solution to Richards equation when the discretization parameters tend to 0. Finally we present some numerical experiments to illustrate the behavior of the method.