Difficulty using .stl and .obj file to make a shell boundary.
 

Hello OpenFoamers,
I have been struggling a lot to make a shell boundary. My case relates to the tutorial case in tutorials/incompressible/simplefoam/rotorDisk in Openfoam8.
The tutorial case uses an OBJ file as a disk and boundary. The boundary is the surfaces of each individual face on a cylinder(3)(inlet/outlet/slipWall).
I'm not able to encounter this error using the snappyHexMesh command on my own OBJ file created using Blender.

--> FOAM FATAL ERROR:
Shell fixed does not support testing for inside
Probably it is not closed.

From function void Foam::shellSurfaces::setAndCheckLevels(Foam::label , const Foam::List<Foam::Tuple2<double, int> >&)
in file shellSurfaces/shellSurfaces.C at line 122.

FOAM exiting

I also tried to split it into different STL files (inlet/outlet/slipWallA/slipWallB).
SlipaWall A&B is semi shell of a cylinder curved surface. Then encountering this issue.

--> FOAM FATAL ERROR:
Shell slipWallA does not support testing for inside
Probably it is not closed.

From function void Foam::shellSurfaces::setAndCheckLevels(Foam::label , const Foam::List<Foam::Tuple2<double, int> >&)
in file shellSurfaces/shellSurfaces.C at line 122.

FOAM exiting

The last way to curb this was to make patch names inside the STL files for different surfaces (inlet/outlet/slipWall). I know how the file read format looks like. But require help, software name, and procedure to obtain patch names.

Please help.:confused: