[gsq]

Hi everyone!
I found a tutorial (https://holzmann-cfd.de/openfoam/ope...-one-way-valve) by Tobias Holzmann. It runs well with its own stl file regionSTL.stl, but when I change it to my stl, snappyHexMesh will generate an extra boundary, defaultFaces, in polyMesh/boundary.
I tried some methods to generate the stl, including adding solid back... end solid in a stl directly, generating five stls from salome Geometry or Mesh and merging them to one. Searched in this forums, I suspect it is because the stl is not closed. After using surfaceCheck, I found it is unclosed. So I used surfaceMeshTriangulate to it. SurfaceMeshTriangulate changed region 'front' to defaultFaces. Even if I changed it back, snappyHexMesh still generated defaultFaces.
The stl and step I used are attached.
Could someone tell me what I should do to generate the stl correctly?
Best regards and thanks in advance