Hello , i use mixed element , Raviart - Thomas and Lagrange, to solve poisson equation. I would like to set boundary values in every Raviart - Thomas element. For example if i have X numbers of faces (or edge in 2D) on one surface i want to set X different boundaries only for Raviart - Thomas elements. Any idea how to solve this? Thank you !!!
Sounds to me like you want something like
DirichletBC(V.sub(0), f, subdomain)
Post a MWE, and describe in more detail what you want to do.