Tutorial partitioned-backwards-facing-step diverges when substeps > 0

[MakisH]

• Tutorials state (last commit / release): 0cd624e
• Operating system (e.g. Linux distribution and version): Ubuntu 22.04
• preCICE Version: develop f42e6c5c
• OpenFOAM adapter branch fix-writing, commit 7f316de6
• OpenFOAM v2306

As discussed in precice/openfoam-adapter#305 (comment) and later, the partitioned backwards facing step tutorial diverges with the default value of substeps.

See the precice-config.xml.

As @davidscn observed, setting <exchange ... substeps="0" /> everywhere seems to give the right results.

In my view, this suggests that either:

• preCICE gives the wrong results with the default value (@BenjaminRodenberg any clue?)
• The OpenFOAM adapter does something wrong

Related to precice/openfoam-adapter#305 and precice/openfoam-adapter#303

[BenjaminRodenberg]

Note that quasi-Newton schemes currently do not support subcycling. A corresponding error is on the way (precice/precice#1721). If the case is somehow doable with constant underrelaxation, you can use subcycling. This would be an important piece of information.

[uekerman]

We also changed the default to substeps="false" now.
precice/precice#1732

[MakisH]

This tutorial now works with preCICE and tutorials from develop.
If I set substeps=true, I do get a helpful error message in the second participant.