Mesh very small geometry
 

I am trying to simulate an air knife. My issue is that the very small features are missed from Snappyhexmesh. I am simply using the FreeCAD CfdOF plugin and am looking for assistance in the SHM flags to make this work.

That is, greatly simplified, a 30mm bore x 100mm long. One end is the inlet at 500kPa air. Along the full length of the bore is a thin protrusion 50um wide and 5mm long. The end of the protrusion 50um x 100mm is open to atmosphere. All other surfaces are no-slip walls.

I have tried to add a mesh refinement to the area in FreeCAD and decrease the base element size and the edge refinement, nothing works. Too small and the meshing crashes. I am yet to mesh the outlet successfully.

Please see the following
https://postimg.cc/JGN8MPz7
https://postimg.cc/GBZgBnXW

Hi


Snappy really is not the right tool for a mesh of this type.
You will be better off using blockMesh, but I would recommend Salome.


Attached are two solutions for making the mesh.
You can import the pipeSlit.py (remove the .txt) in Salome.
You can compute the mesh and extrude it.
Salome will automatically create boundary names for you.
Edge groups will become facegroups when extruded.