Hello,
I can confirm that the preCICE coupling interFoam or interIsoFoam with CalculiX works, but we had to use an adaption of the force estimation for OpenFOAM according maoxm’s fix in https://github.com/precice/openfoam-adapter/issues/127 for preCICE 2.0. Otherwise the forces have been by a factor of 1000 too large, most likely due to an unnecessary multiplication of the pressure with the fluid density which is not required for inter*FOAM even if it is an incompressible solver in OpenFOAM terminology.
Ulrich