Not specific error message when running FSI simulations using *MODAL DYNAMIC solution.

[martinsaravia]

Hi guys,

We have found that in order to use a *MODAL DYNAMIC solution in Calculix it is neccessary to run first the *FREQUENCY extraction step in a sepparate .inp file. If we try to run a case in which the frequency extraction step and the modal dynamic step are in the same .inp file, the adapter gives the error: "ERROR: Only thermal coupling or FSI is available with preCICE", which is not specific. The line of this error is 1509 of ccx_2.20.c (https://github.com/precice/calculix-adapter/blob/master/ccx_2.20.c). Again, if we first run a simulation extracting the modes and frequencies (and generating the .eig file with modal data) and then run the modal dynamic analysis in another .inp file, everything works fine.

This is not clear in the Modal Dynamic Simulations section of the adapter's page (https://precice.org/adapter-calculix-config.html). I think it could be helpful to make clear that the frequency step and the modal dynamic step must be in different .inp files. Also, the last sentence in the help is confusing, it states "Note that reading displacements is not supported in these simulations." Actually the adapter is reading the displacement, so this is confusing. There is no reason why the displacement information taken from a modal dynamic simulation would be different from a traditional *DYNAMIC step since Calculix should reconstruct the structure displacement field in terms of the modal shapes and the generalized coordinates (which are the degress of freedom in a *MODAL DYNAMIC simulation).