How to create inlet/outlet/wall STL files from a STL CAD model
 

I had some troubles trying to define the inlet/outlet/wall STL files from a CAD model that I have created.
So basically I designed a cylinder and I saved it as a STL file which rappresents the volume where I want to perform my CFD simulation using OPENFOAM. Now I would like to extract the STL files of the inlet (bottom of the cylinder), the outlet (top of the cylinder) and the external wall (sorrounding area of the cylinder) so that I can set up the boundary conditions.

What should I do in order to extract them?

This question has come up after watching the following youtube video https://www.youtube.com/watch?v=ObsFQUiVi1U where I decided to replicate the same tutorial starting from scratch, that is from the CAD model itself. As I said previously I can get the solid volume but I don't know how to extract the inlet/outlet/wall surfaces as STL files.

Does anyone have any suggestion?

PS: I've been using Solid-Edge, Solid-Works and CREO as CAD softwares but without success.

I just found out a possible way to do it: let's say for example that you are using Solide-Edge and you've created your model; what you could do is save it as a .igs file and then import it to Salome Meca and use the Create Group option in order to select the surfaces you are intereseted on. Afterwards you can save separately all the parts you need (volumes and faces) in the .STL format as desired.