[七辆战车]

These days i was trying to simulate two floating bodies in the water by OpenFOAMv1906 (no constraints), but i found some difficulties:
First one is i added two bodies in the dynamicMeshDict like this:
sixDoFRigidBodyMotionCoeffs
{
bodies
{
floatingObject1
{
patches (floatingObject1);
...
centreOfMass (...)
...
}
floatingObject2
{
patches (floatingObject1);
...
centreOfMass (...)
...
}
}
}
and when i was running Application, it noted "cannot find centreOfMass", only i deleted "bodies" and "floatingObject1" in the above file can it work, however, the outcome was that only floatingObject2 got work, so i don't know where the problems are.
And second one is how can i connect two floating bodies by one spring? I tried to use linearSpring in the "restraints", but it's said that linearSpring can only connect anchored point with refAttachmentPt, is this right? If not, how can i do to connect two floating bodies?
Thank you for your answering!