# Validating neumann condition in dolfinx

**URL:** <https://fenicsproject.discourse.group/t/validating-neumann-condition-in-dolfinx/8732>\
**Category:** variational formulation\
**Created:** [July 8, 2022, 12:52am UTC](https://fenicsproject.discourse.group/t/validating-neumann-condition-in-dolfinx/8732 "2022-07-08T00:52:46Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![leshinka](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/leshinka/32/5789_2.png) [@leshinka](https://fenicsproject.discourse.group/u/leshinka)\
**Post date:** [July 8, 2022, 12:52am UTC](https://fenicsproject.discourse.group/t/validating-neumann-condition-in-dolfinx/8732/1 "2022-07-08T00:52:46Z")

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I have solved a PDE and would like to confirm that the neumann boundary conditions are correctly applied. Solution post [How to check that the Neumann boundary condition is correctly applied - #4 by nate](https://fenicsproject.discourse.group/t/how-to-check-that-the-neumann-boundary-condition-is-correctly-applied/7632/4) gives a way to do this in old `dolfin`. The syntax changed in non-intuitive manner. Anyone knows how to translate the solution to `dolfinx`?

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**Author:** ![dokken](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/dokken/32/1560_2.png) [@dokken](https://fenicsproject.discourse.group/u/dokken)\
**Post date:** [July 8, 2022, 7:44am UTC](https://fenicsproject.discourse.group/t/validating-neumann-condition-in-dolfinx/8732/2 "2022-07-08T07:44:05Z")

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What do you mean by

> [@leshinka](#):
>
> The syntax changed in non-intuitive manner.

How to compute boundary integrals are for instance covered in:  
[https://jorgensd.github.io/dolfinx-tutorial/chapter2/ns\_code2.html#verification-of-the-implementation-compute-known-physical-quantities](https://jorgensd.github.io/dolfinx-tutorial/chapter2/ns_code2.html#verification-of-the-implementation-compute-known-physical-quantities)