I was looking at the pimpleFoam/RAS/rotatingFanInRoom tutorial, and there was an STL file "AMI" in its resources. When you run snappyHexMesh, it generates 2 patches, a static and a rotating cylinder. The 2 patches are called AMI and AMI_slave, but there is only 1 AMI stl file. How do you create 2 patches (or named surfaces) from the same surface in say Freecad?