# Breaking-dam-2d crashes when using \*MODAL DYNAMIC in CalculiX

**URL:** <https://precice.discourse.group/t/breaking-dam-2d-crashes-when-using-modal-dynamic-in-calculix/3005>\
**Category:** Official adapters and tutorials\
**Tags:** openfoam, calculix, fsi\
**Created:** [September 23, 2026, 11:18am UTC](https://precice.discourse.group/t/breaking-dam-2d-crashes-when-using-modal-dynamic-in-calculix/3005 "2026-09-23T11:18:49Z")\
**Posts on this page:** 1\
**Showing post:** 2

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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:** [September 26, 2026, 4:11pm UTC](https://precice.discourse.group/t/breaking-dam-2d-crashes-when-using-modal-dynamic-in-calculix/3005/2 "2026-09-26T16:11:34Z")

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Hi @Bianca_Gritti,

we don’t have much experience with this feature, and we don’t have a tutorial either. Any observations or further input here would be very useful to improve the support, and rarely (if at all) someone asks for it, so I see potential here.

You probably already saw the documentation section of the CalculiX adapter, which is mostly there as a hint, rather than a tested feature:

> **[Configure the CalculiX adapter](https://precice.org/adapter-calculix-config.html)**
>
> Write a config.yml, write a CalculiX case input file, and run an adapted CalculiX executable.

Since the breaking-dam-2d tutorial is also known to have issues when running in parallel (see [Breaking dam 2D fails in parallel · Issue #710 · precice/tutorials · GitHub](https://github.com/precice/tutorials/issues/710)), I would recommend starting with the perpendicular-flap. Does that work fine for you?

When the feature was developed, it was tested with the perpendicular-flap tutorial and with implicit coupling, but it has not seen much activity since then. One of the related PRs:

> <https://github.com/precice/calculix-adapter/issues/93>
>
> Since https://github.com/precice/calculix-adapter/pull/91, the adapter supports …modal dynamic simulations. (Where we use pre-computed eigenmode decomposition to speedup the computations by projecting forces into these modes and solving harmonic oscillators)
> However, this functionality was designed with explicit coupling in mind and doesn't work with implicit coupling. It seems null displacements are generated. I added a warning message until we fix this.

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