Did a quick test. Didn't use as large of a fence as you did cd. I also made it "flush" with the side of the car rather than the fender. There is a speed discrepancy between the two runs. I only made the 2 runs as well. It's only 10 seconds long so you might want to adjust the playback speed. I forgot to get a picture of the piece I used while it was attached so it is kind of loosely in place.
I think the tufts look better without it. With it the side tufts are all pointing more vertical than the stock version. Stock they seem a little more steady as well, but that could just be the speed difference.
It is interesting that the windshield tufts seem unaffected by the fence. I would think the lower 2 (you can't see the top 3 in the stock version, but they closely match) would be pointing more up or more unsteady.
I was curious if I could attempt to ID the vortex (if present) from the A-pillar by using a small rod/stiff wire and a tuft to see what is happening a few inches off the surface. I couldn't find the coat hanger I was thinking of so I gave up on it for now. I might revisit that idea eventually though.
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1973 Fiat 124 Special
1975 Honda Civic CVCC 4spd
1981 Kawasaki KZ750E
1981 Kawasaki KZ650 CSR
1983 Kawasaki KZ1100-A3
1986 Nissan 300zx Turbo 5 spd
1995 Chevy Astro RWD (current project)
1995 Mercury Tracer
2017 Kawasaki VersysX 300
2022 Corolla Hatchback 6MT
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