There are holes on the mesh surface

After I built the 3D model, I divided the mesh, but holes appeared on the surface of the mesh. *As shown in the picture below, how can I solve this problem?

11.16.mfx (8.1 KB)
@cgw @jeff.dietiker

Please attach your stl file.

3D.stl (19.9 KB)

You have some very long triangles that fall below the tolerance (angle less than 0.1 degree).

 Total number of facets read =   406
 Number of valid facets      =   393
 Number of ignored facets    =    13

This is a common issue many people miss. I think we will make this a fatal error to force inspection of the stl file. You can set the facet angle tolerance to 0.0 to keep all triangles.

You will get better intersection at the inlet and outlet if you let the stl file stick out of the domain in the z-direction. Remember to set gravity in the negative z-direction after meshing if z is your vertical direction.

Thank you!I will try it.