https://research.chalmers.se/publica...2_Fulltext.pdf
Is this the study? I found it in another of your posts. Great find! I was glad to see the authors address wheel venting and the total contribution to aerodynamic drag. I have experimented with fully covered rims on my Golf and found no measurable improvement. I suspect it interferes with flow out of the front wheel wells and creates greater lift/drag.
P.S. This probably should be posted in Aerodynamics. If you contact a moderator they can move it for you.