Dirichlet and Boundary conditions in Darcy tutorial.

Hi @fverdugo ... I think that the Dirichlet and Neumann Boundary conditions are flipped in the Darcy's tutorial + RT FEs.

In particular, in the Darcy problem, one imposes the trace of the pressure in the Dirichlet boundary, and the normal component of the flux in the Neumann boundary. Indeed, Dirichlet boundary conditions are natural boundary conditions (i.e., imposed weakly) for Darcy, and Neumann boundary condition are essential boundary conditions for Darcy (i.e., imposed strongly).

See, e.g., pag. 153 of

https://team-pancho.github.io/documents/anIntro2FEM_2015.pdf

Is there anything I am missing here? Do you agree? I can help with the changes required to fix this, if needed.

Localisez le tutoriel Darcy et ses exemples d’éléments finis de Raviart–Thomas, puis comparez les descriptions des conditions aux limites et leur implémentation avec la référence FEM citée dans l’issue. La tâche est terminée lorsque l’explication du tutoriel et les exemples concernés correspondent systématiquement à la formulation Darcy prévue.

Rédigé par le modèle d'indexation à partir du texte de l'issue.