Hi Charger,

I helped mesh a centrifugal compressor that had a spinning impeller inside a an axial-inlet, volute-outlet housing. In the airspace between the impeller and the housing, a surface could be constructed that split the fluid and a "sliding mesh" method allowed the elements around the impeller to rotate, while the elements in the volute were stationary.

Since the screw pump has one screw rotating CW and an interleaved screw rotating CCW, there is no fixed boundary to use the "sliding mesh" method.

SOLIDWORKS uses Parasolid as its geometry kernel, and so does SIEMENS NX11, where I have the skills to quickly clean up geometry for meshing. Parasolid is also the geometry kernel for DesignModeler. What this means is that there is no translation from one geometry kernel to another when moving geometry between those three systems. Things can go wrong when the geometry has to be translated into another kernel, such as ACIS, which is what SpaceClaim uses. See this example.

I downloaded the lobe pump example to get an understanding of what kind of mesh the solver works with. Now I know there is the "Immersed Body" method in CFX so I have updated the geometry to have the two screws and the boundary solid. This is analogous to the lobe pump. I don't have a CFX license to use in Version 15, only the newer Student licenses that are available. Attached is the updated Version 15 geometry suitable for "Immersed Solid" method.

Question for the CFX experts: If the boundary is meshed with tetrahedral, do the immersed solid bodies need to also be meshed with tetrahedral elements or can they by hex meshes?

Here is how I used the Geometry file: I linked three Mesh components, then suppressed two of the three solids to mesh a single solid. I exported three Fluent format mesh files, which I was able to import into CFX 19.1

Cheers,

Peter