Quote:
Originally Posted by j-c-c
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?
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Wire has a drag coefficient of Cd 1.17, higher than a sheet of plywood, crossways in the wind. If you did the grid you'd want to use as 'small' a wire as you could find. Like a 0.008 #1 guitar string or piano wire.
Long ago, the bi-planes used 'streamline' wire for all the tension bracing between the two wings, and it was designed for low-drag, with a 'teardrop' cross-section. Wicks, or one of the other catalog stores for experimental aircraft supplies might be a source. Don't know.
A problem with it is that, if the airflow is not 'parallel' to it's symmetrical streamlined chord profile, you'll get separated flow, and the turbulence will affect what the tufts are 'telling' you.
For the mirrors, the 'tennis racket' is a very good idea. If the wire is properly 'stretched', where they cross, will not require bonding, as in wire fabric.
In my wind tunnel, I use hollow aluminum radio-controlled aircraft wing strut from hobby shops to attach my yarn to, and then rotate it in the airstream to see at what angle of attack the flow is actually moving, then I know that I'm getting as good a flow representation as I'm likely to get.
For the front of the car, you could create a 'holder', which is mounted outboard of the body, like is done with 'Go-Pros', and extend the strut 'into' the footprint of the nose from there, taking care to 'aim' it.
In a wind tunnel, you'd just use a propylene glycol smoke generator and wand ( a vey large 'vape' ).
For the back of the car, do as was already mentioned about Lightyear.