# Question about Neumann boundary conditions

**URL:** <https://getfem.discourse.group/t/question-about-neumann-boundary-conditions/95>\
**Category:** General\
**Created:** [July 20, 2025, 4:25pm UTC](https://getfem.discourse.group/t/question-about-neumann-boundary-conditions/95 "2025-07-20T16:25:18Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![EricAComstock](https://yyz2.discourse-cdn.com/free1/user_avatar/getfem.discourse.group/ericacomstock/32/68_2.png) [@EricAComstock](https://getfem.discourse.group/u/EricAComstock)\
**Post date:** [July 20, 2025, 4:25pm UTC](https://getfem.discourse.group/t/question-about-neumann-boundary-conditions/95/1 "2025-07-20T16:25:18Z")

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Hello All,

Just to confirm, the BC

```auto
md.add_source_term_brick(mim, 'f', 'zeros', 45)

```

will add a boundary condition requiring the derivative of f to be zero across the boundary at boundary 45, correct? I want to make sure in case there is some other thing I am missing, since right now my results do not have the derivative of f being zero at this boundary.

Sincerely,  
Eric Comstock

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<div class="post-metadata">

**Author:** ![Konstantinos.Poulios](https://avatars.discourse-cdn.com/v4/letter/k/ac91a4/32.png) [@Konstantinos.Poulios](https://getfem.discourse.group/u/Konstantinos.Poulios)\
**Post date:** [July 22, 2025, 11:43am UTC](https://getfem.discourse.group/t/question-about-neumann-boundary-conditions/95/2 "2025-07-22T11:43:57Z")

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adding a source term with zeros is the same as if you do not add any source term.

You need to add the term only if the gradient is not zero, like in this example:

[https://scicomp.stackexchange.com/questions/44229/how-to-constraint-the-tangential-gradient-on-a-boundary-in-fenics/44250#44250](https://scicomp.stackexchange.com/questions/44229/how-to-constraint-the-tangential-gradient-on-a-boundary-in-fenics/44250#44250)