# Fail with a very basic 3d mesh

**URL:** <https://community.freefem.org/t/fail-with-a-very-basic-3d-mesh/2348>\
**Category:** General Discussion\
**Created:** [March 21, 2023, 5:28pm UTC](https://community.freefem.org/t/fail-with-a-very-basic-3d-mesh/2348 "2023-03-21T17:28:58Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![mrbenson](https://avatars.discourse-cdn.com/v4/letter/m/d07c76/32.png) [@mrbenson](https://community.freefem.org/u/mrbenson)\
**Post date:** [March 21, 2023, 5:28pm UTC](https://community.freefem.org/t/fail-with-a-very-basic-3d-mesh/2348/1 "2023-03-21T17:28:59Z")

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Hi,

I just tried a very simple 3d steady-state thermal problem :

- two solids, each has a specific thermal conductivity
- two mixed boundary conditions for each thermal space has a specific conductance hi and an external temperature Ti, such the flux is : - lambda\*dn(T) = hi.(Ti-T).

In my case, the two temperatures are 0°C and 20°C, and I do not understand why the temperature is completely wrong, going to -2883 to 5393 !

Is there something wrong in the msh file (the msh file comes from netgen mesher) ?

Best regards.

[test.zip](https://community.freefem.org/uploads/short-url/j4OzAN4nIaEthdnT0xjPWb6Ao0l.zip) (28.9 KB)