# Raviart Thomas boundary condition

**URL:** <https://fenicsproject.discourse.group/t/raviart-thomas-boundary-condition/2409>\
**Category:** Uncategorized\
**Created:** [February 11, 2020, 10:38am UTC](https://fenicsproject.discourse.group/t/raviart-thomas-boundary-condition/2409 "2020-02-11T10:38:46Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![odysgros](https://avatars.discourse-cdn.com/v4/letter/o/ba9def/32.png) [@odysgros](https://fenicsproject.discourse.group/u/odysgros)\
**Post date:** [February 11, 2020, 10:38am UTC](https://fenicsproject.discourse.group/t/raviart-thomas-boundary-condition/2409/1 "2020-02-11T10:38:46Z")

</div>

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 !!!

---

<div class="post-metadata">

**Author:** ![volkerk](https://avatars.discourse-cdn.com/v4/letter/v/9d8465/32.png) [@volkerk](https://fenicsproject.discourse.group/u/volkerk)\
**Post date:** [February 12, 2020, 9:18am UTC](https://fenicsproject.discourse.group/t/raviart-thomas-boundary-condition/2409/2 "2020-02-12T09:18:04Z")

</div>

Sounds to me like you want something like

```python
DirichletBC(V.sub(0), f, subdomain)

```

Post a MWE, and describe in more detail what you want to do.