Would this test set-up be informative?
 

It's not something I have seen or read about. It seems wool tuff testing is useful but often seems to be mainly 2d in its results. I'm wondering if a say 1/2" thin wire but rigid multicolored tuff grid (tuffs attached at nodes on the grind), say 24" square, mounted perpendicular to air flow might give a clearer picture of airflow around say a door mounted mirror if placed slightly down wind, or say mounted just in front of the leading edge of the grille intake/hood/bumper area, or any location to gather a clearer picture of air flow, short of a computer..
My concern is, how much the thin wire grid would distort the takeaway.
Worth a try?

It's been done. Maybe someone will come along with an example or results.

Well, if it has been done, it must not be very useful or informative, and I have never heard it referred to on this site, which should speak volumes?

Try 1-2 thousandths of an inch.

I've had some time to search be not much success:

https://www.researchgate.net/profile...he-area-of.png
www.researchgate.net/figure/Tuft-flow-visualization-in-the-wind-tunnel-experimental-vein-highlighting-the-area-of_fig3_292208380

This was in a wind tunnel. I know I've seen a picture of a 6x6ft grid hitch-mounted behind a moving vehicle, but I can't prove it.

Cumbersome, only works trailing the vehicle; it may show the size of the wake but not the extent.

I like the idea of tiny, smoke-filled soap bubbles.

No success yet on finding any prefab grid mesh of that gauge, especially in purchased useful sizes ( ie 100ft min).
I was thinking of more like .030" SS Tig welding rod, dipped into epoxy (for node connections) with a 3/4"? square opening, attached to a 4 sided aero shaped tube now rectangular frame, with attaching points for suction cup mounts, etc.
I like the TIG rod solution as its straight, rigid, and I can oven burn off the tuffs and their glues when grid needs to be re-tuffed.
So my main concern, will .030 be useful here, or do I need a better solution? I get smaller is better.
But it does seem the individual tuffs will far exceed the FA than the wire mounting will.

Is my assumption you feel that any upwind testing as I noted has little merit with this proposed rig?

It's all speculation, of course. Have you ever been in a wind tunnel? They (Darko) use[d] a fabric mesh to calm the air at the throat of the tunnel.

https://ecomodder.com/forum/member-f...6-100-1191.jpg

Tufts on a grid on a mesh might work. A circular hoop strung like a badminton racket might do better.Who knows?

Well, the idea here is to visualize disturbed air, not to calm it, and not to further disturb it, I believe.
I really do like the hand held badminton wool tuff concept. Kind of like a basic multi point additive smoke wand. Interesting.
And yes, I have visited two in use wind tunnels, at GT and Windshear.

Lightyear One engineers used a custom rake with pressure probes to measure the wake. They also installed one near the rear quarter.

https://www.youtube.com/watch?v=CI8BkK3ycYo

A bit harder to visualize real time and way above my budget.

At least it's real world and not in a wind tunnel.