# Non matching meshes

**URL:** <https://community.freefem.org/t/non-matching-meshes/1198>\
**Category:** General Discussion\
**Created:** [September 10, 2021, 12:44pm UTC](https://community.freefem.org/t/non-matching-meshes/1198 "2021-09-10T12:44:46Z")\
**Posts on this page:** 3\
**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:** [September 10, 2021, 12:44pm UTC](https://community.freefem.org/t/non-matching-meshes/1198/1 "2021-09-10T12:44:46Z")

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Hi,  
Is there a way to handle non-matching meshes (with no overlaps) with freefem. I have a very basic laplacian test case, two squares meshed independly but sharing a common boundary (same tag). I read that mortar method could do the job using lagrangian multiplier to enforce continuity condition \int\_{\Gamma}(u\_1-u\_2)=0, where u\_i are the restriction of u on each side of the border but i can’t see how to do that… Any idea ?

best reragds.

PS : it’s a classical lapacian with u=0 on Gamma tag=1 and u=1 Gamma tag=2, dn(u)=0 on Gamma tag 3.  
Processing: square.msh…  
[square.zip](https://community.freefem.org/uploads/short-url/xaiinVlsGtRH7ztBoDu5lPT5mgj.zip) (17.1 KB)

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**Author:** ![DuanXY](https://avatars.discourse-cdn.com/v4/letter/d/5fc32e/32.png) [@DuanXY](https://community.freefem.org/u/DuanXY)\
**Post date:** [November 29, 2021, 6:52am UTC](https://community.freefem.org/t/non-matching-meshes/1198/2 "2021-11-29T06:52:22Z")

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Hi,  
I meet the same problem as you!  
Have you solved the problem successfully?

best regards.

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**Author:** ![sumantkr](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/sumantkr/32/2681_2.png) [@sumantkr](https://community.freefem.org/u/sumantkr)\
**Post date:** [December 1, 2021, 6:00am UTC](https://community.freefem.org/t/non-matching-meshes/1198/3 "2021-12-01T06:00:23Z")

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Hello @mrbenson  
I am also working on the interface problem with the different material properties of each sub-domains.

If you have solved this non-matching interface problem then please comment on the pseudo-steps followed by you.

Any supporting documents will be also helpful for me.

Thanks!!!