# Homogeneous Neumann Boundary condition

**URL:** <https://community.freefem.org/t/homogeneous-neumann-boundary-condition/318>\
**Category:** General Discussion\
**Created:** [April 5, 2020, 5:32pm UTC](https://community.freefem.org/t/homogeneous-neumann-boundary-condition/318 "2020-04-05T17:32:09Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![paolopiers](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/paolopiers/32/48_2.png) [@paolopiers](https://community.freefem.org/u/paolopiers)\
**Post date:** [April 5, 2020, 5:32pm UTC](https://community.freefem.org/t/homogeneous-neumann-boundary-condition/318/1 "2020-04-05T17:32:09Z")

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Hello everyone,  
I was trying to implement in FreeFem the variational formulation for the biharmonic equation in H^2\_0(omega) (see Theorem 6.8-3 of P. G. Ciarlet - Linear and Nonlinear Functional Analysis with Applications, Philadelphia, 2013).

I searched for the answer in the previously opened topics but I could not find anything.  
Could you please help me solve the problem described below?

I mesh my domain (say the unit disk) using a Hsieh-Clough-Torcher element (Element\_HCT).  
The bilinear and linear forms are very easy to write. What I cannot implement is the homogeneous Neumann boundary condition along the entire boundary.

In this case, indeed, the strategy making use of the command `int1d(Th,borderLabel)(dnu*testFunc)`, where `dun` is a prescribed function and `testFunc` is a generic test function, is not implementable since we always have `dnu=0`. How would you solve this?

Many thanks in advance and best regards,

Paolo

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**Author:** ![mps](https://avatars.discourse-cdn.com/v4/letter/m/67e7ee/32.png) [@mps](https://community.freefem.org/u/mps)\
**Post date:** [December 28, 2022, 3:28pm UTC](https://community.freefem.org/t/homogeneous-neumann-boundary-condition/318/2 "2022-12-28T15:28:58Z")

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Hi,  
did you find any solution by chance?

Marco