# Collapsible Tube (OpenFOAM+CalculiX)

**URL:** <https://precice.discourse.group/t/collapsible-tube-openfoam-calculix/1334>\
**Category:** Official adapters and tutorials\
**Tags:** openfoam, calculix, fsi\
**Created:** [March 20, 2023, 3:50pm UTC](https://precice.discourse.group/t/collapsible-tube-openfoam-calculix/1334 "2023-03-20T15:50:59Z")\
**Posts on this page:** 1\
**Showing post:** 21

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**Author:** ![Makis](https://yyz2.discourse-cdn.com/free1/user_avatar/precice.discourse.group/makis/32/25_2.png) [@Makis](https://precice.discourse.group/u/Makis)\
**Post date:** [March 30, 2023, 10:03am UTC](https://precice.discourse.group/t/collapsible-tube-openfoam-calculix/1334/21 "2023-03-30T10:03:38Z")

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> [@mishal49](#):
>
> I did however, try taking the elastic pipe and imposing the same boundary conditions.

Good strategy! You could even use ASTE to mock the other participant: [Artificial Solver Testing Environment (ASTE) | preCICE - The Coupling Library](https://precice.org/tooling-aste.html#replay-mode) (even though it currently only works with explicit schemes).

> [@mishal49](#):
>
> The case ran fine so this brings me to question whether the mesh types of the fluid and solid matter. Do they have to be the same type?

No. The participants know nothing about each other’s internals (including their mesh) and you don’t need conforming meshes on the interface: that’s what data mapping is for.

> [@mishal49](#):
>
> Do they have to be coarse because a finer mesh might be more likely to get twisted?

Generally, the mesh resolution is defined by the needs of the solvers themselves. Most commonly, we use much finer fluid meshes than solid meshes, just because usually flows are much more complex than solid dynamics.

> [@mishal49](#):
>
> Do I change the solver in dynamicmeshdict based on my mesh types maybe?

This is indeed a much more important point. By default, we use displacementLaplacian in our OpenFOAM tutorials, which is a rather simple mesh motion solver, that does not perform so well. But it just works most of the time.

If your mesh gets too skewed, then you could try, e.g., RBFMeshMotionSolver: [Mesh Solver OpenFOAM Error - #10 by Makis](https://precice.discourse.group/t/mesh-solver-openfoam-error/1130/10)

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