# Boundary Conditions at Free Surfaces

**URL:** <https://calculix.discourse.group/t/boundary-conditions-at-free-surfaces/148>\
**Category:** Uncategorized\
**Created:** [September 1, 2020, 5:35pm UTC](https://calculix.discourse.group/t/boundary-conditions-at-free-surfaces/148 "2020-09-01T17:35:28Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Sangeet](https://avatars.discourse-cdn.com/v4/letter/s/b19c9b/32.png) [@Sangeet](https://calculix.discourse.group/u/Sangeet)\
**Post date:** [September 1, 2020, 5:35pm UTC](https://calculix.discourse.group/t/boundary-conditions-at-free-surfaces/148/1 "2020-09-01T17:35:28Z")

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Hello everyone! I am a graduate student working on fluid structure thermal interactions and I am currently looking at Calculix for FEM.

I am sorry if the question is too trivial but I was wondering what’s the boundary condition that Calculix imposes on the free boundary surfaces where I haven’t specified a load or a prescribed displacement. Or are there no boundary conditions applied?

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**Author:** ![mkraska](https://avatars.discourse-cdn.com/v4/letter/m/96bed5/32.png) [@mkraska](https://calculix.discourse.group/u/mkraska)\
**Post date:** [September 2, 2020, 2:41pm UTC](https://calculix.discourse.group/t/boundary-conditions-at-free-surfaces/148/2 "2020-09-02T14:41:12Z")

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Then you essentially apply a no-load (traction-free) and unconstrained displacement condition.

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**Author:** ![Sangeet](https://avatars.discourse-cdn.com/v4/letter/s/b19c9b/32.png) [@Sangeet](https://calculix.discourse.group/u/Sangeet)\
**Post date:** [September 4, 2020, 7:02am UTC](https://calculix.discourse.group/t/boundary-conditions-at-free-surfaces/148/3 "2020-09-04T07:02:57Z")

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That makes sense. Thank you for clearing that up.