# 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:** 23

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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, 7:41pm UTC](https://precice.discourse.group/t/collapsible-tube-openfoam-calculix/1334/23 "2023-03-30T19:41:38Z")

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Why are you not exchanging and reading displacements in the fluid side?  
Note that you need `DisplacementDelta` (displacements relative to the last coupling time window), in contrast to `Displacement` (relative to the original reference point).

Which brings me to the question: does the fluid simulation itself (without coupling, since anyway OpenFOAM does not read anything) converge?

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