# Normal boundary condition

**URL:** <https://community.freefem.org/t/normal-boundary-condition/341>\
**Category:** General Discussion\
**Created:** [April 10, 2020, 1:55pm UTC](https://community.freefem.org/t/normal-boundary-condition/341 "2020-04-10T13:55:58Z")\
**Posts on this page:** 1\
**Showing post:** 3

<div class="post-metadata">

**Author:** ![michaellevitin](https://avatars.discourse-cdn.com/v4/letter/m/46a35a/32.png) [@michaellevitin](https://community.freefem.org/u/michaellevitin)\
**Post date:** [April 14, 2020, 11:30am UTC](https://community.freefem.org/t/normal-boundary-condition/341/3 "2020-04-14T11:30:20Z")

</div>

Thanks, Paolo! It is not exactly what I need - I am solving a vector eigenvalue problem for elasticity, see [FreeFem manual](https://doc.freefem.org/tutorials/elasticity.html) and want to impose mixed boundary conditions: tangential component of traction to vanish (which is automatic due to the weak formulation), and the normal component of the vector field `[u,v]`, that is `u*N.x+v*N.y` to vanish as well. It’s the second one I’m struggling with.  
M.

---

_[View the full topic](https://community.freefem.org/t/normal-boundary-condition/341)._