Thanks for the explanation. I did find how to generate flux report in Fluent, but then I got even more confused, becuase
(1) the flux value calculated in Fluent doesn't match the [radial velocity * area] value on the same surface in CFD post;
(2) the flux values don't match the trend I see from the streamline/pathline plot.
For the 2nd point, see figures below: this is part of my streamline plot, which I use for a qualitative visual comparison; I add a red arrow to show that the centripetal direction is the flow I want. The visual difference between flow going in Zone 1 and Zone 2 is very huge, definitely more flow going into Zone 1 than Zone 2. I undertsand that streamline is probably an exaggerated comparision since it is not showing all the flows. But after I generated the flux report in Fluent, I found the flux value in Zone 2 is actually higher than Zone 1.
If using the method of radial velocity multiplied by area in CFD post, I got higher flux in Zone 1 than Zone 2, same trend with streamline, although the difference is much smaller than I expected.
I'm very confused now: is my interpretation of the streamline plot wrong? And why did CFD post and fluent give me opposite trends?