# Problems with building an adapter between 'sixDOFmotion solver' and 'CalculiX'

**URL:** <https://precice.discourse.group/t/problems-with-building-an-adapter-between-sixdofmotion-solver-and-calculix/536>\
**Category:** Official adapters and tutorials\
**Tags:** openfoam, adapters, calculix, fsi\
**Created:** [March 31, 2021, 8:20pm UTC](https://precice.discourse.group/t/problems-with-building-an-adapter-between-sixdofmotion-solver-and-calculix/536 "2021-03-31T20:20:15Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![uekerman](https://yyz2.discourse-cdn.com/free1/user_avatar/precice.discourse.group/uekerman/32/2199_2.png) [@uekerman](https://precice.discourse.group/u/uekerman)\
**Post date:** [April 6, 2021, 7:26am UTC](https://precice.discourse.group/t/problems-with-building-an-adapter-between-sixdofmotion-solver-and-calculix/536/2 "2021-04-06T07:26:46Z")

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Hi Yujia,

That’s an interesting case that you try to realize. Thanks for the detailed description. I think I got it.

> [@YujiaWei2020](#):
>
> sixDOFrigidbodymotion solver is basically a library, there is no main function in its .C file. I can only find its simulation loop, where and how should I insert the preCICE API？Do I need to write another member function in the sixDOFrigidbodymotion class and call in interFoam?

Here, I am lacking a bit OpenFOAM know-how, but I am not sure whether you can really run the rigid-body solver in OpenFOAM as a stand-alone solver. I thought it’s just some feature you can use in fluid solvers to do rigid-body FSI. So it would be two solvers you want to couple: interDyFoam and CalculiX, where you use the rigid-body FSI feature within interDyFoam and a structure-structure coupling between both. But I could be wrong.

I have a different suggestion. Why don’t you solve the whole structure directly in CalculiX? I guess you could use a very coarse mesh in the rigig-body part of the domain (maybe even only a single element?) and simply use a non-homogeneous material with infinity stiffness in the rigid part. Maybe you get an ill-conditioned problem then, but might be sth to ask in the [CalculiX Forum](https://calculix.discourse.group/). In contrast to the solution above, this suggestion should be much easier to simply try out.

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