Question about flow simulation wizard

The only reference axis I have ever used is with respect to a rotating reference frame - is this what you are referring to?

This is from the SolidWorks Knowledgebase; S-024540, it was last updated in 2012 so should be current i believe.

There are really only two cases that might require the reference axis to be used.

1) The first is for an analysis that requires the Rotation option.

Select the Rotation check box if you want to specify either Local region(s) of rotation or the Global rotating reference frame. For a Global rotating reference frame you need to specify the Reference axis and the Angular velocity.

2) The second is if you are entering a formula or table of data to describe a boundary condition.

Specify the Reference axis of the global coordinate system (X, Y or Z). This axis is used in the Dependency dialog box for specifying data as tabular or formula dependencies on the R coordinate reckoned in a cylindrical coordinate system.from the reference axis.