Here's a good post from the GTAC team that Jerry found and I decided to add as a topic to this resource library.
90% of the time taken to do CFD analysis is in pre-processing mostly because we're always concerned with internal or external volumes around an object... for which we never have the CAD. More than any other type of analyst, CFD analysts must care about CAD and with NX we make it pretty easy to create these flow volumes and here's how!
Following is another great article from the Siemens PLM GTAC team.
NX Flow solver in Advanced Simulation requires all elements used in modeling Flow to be 3D elements. While the solid mesh for a design part occupies the part itself, the fluid mesh occupies the void between the bodies. Because the void itself is not a body, one must create a solid body to occupy the void. This solid body is generated in the idealized part I and then a mesh is applied on this body with 3D fluid elements using the NX meshing tools. This internal fluid volume can be created by one of the following 3 methods:
In this article we will go over the 3rd method specified above to extract the flow volume. Consider the task of extracting the internal flow volume in the following valve:
Here are the steps to extract the internal volume:
Thanks to SR for the tip.