Has anyone used Flow Visualization Paint
03-02-2019, 10:50 PM
#11
Whats your dimensions? I'm 6'3" 220# athletic build, Long legs, short torso and wide shoulders and a 6'5"-6'6" reach. It was a bitch to build a seat rail to fit the car for me but with my Sparco Evo 2 with the fiberglass on the floor pan and against the rear bulkhead I fit wonderfully. Fine enough for a handful of 2-3 hour drives on the street while I've had the car.
03-04-2019, 11:16 AM
#13
03-04-2019, 11:35 AM
#14
Not really very useful unless you are trying to see how airflow stays attached over a larger surface area (like the side of an F1 car). This is done more for validation of CFD really to make sure there aren't any flows they weren't able to properly simulate disrupting their designs.
Also, JESUS FUKING CHRIST I swear to ****ing god if he mentions "late models" one more gawd damn time...
Also, JESUS FUKING CHRIST I swear to ****ing god if he mentions "late models" one more gawd damn time...
03-04-2019, 11:40 AM
#15
Being an aero engineer, I actually enjoyed this thread. There aren't many cost effective ways to run CFD on a car and it was a worthwhile thought.
Instead of complaining about someone else's thread, create your own to liven up this place.
Instead of complaining about someone else's thread, create your own to liven up this place.
03-04-2019, 12:33 PM
#17
Phoenix is suuuuuuper expensive. I'm planning out a corvette track car build myself at the moment. Definitely not having them do anything, despite them being 2 minutes from my house.
For what it's worth, I enjoy these threads. I think the only real indicator of how good your aero is for hobbyists like us is lap times or other data like cornering speed though.
For what it's worth, I enjoy these threads. I think the only real indicator of how good your aero is for hobbyists like us is lap times or other data like cornering speed though.
03-04-2019, 01:02 PM
#18
Registered User
I can see some potential usefulness if you're comparing end plates for a wing, or some other very simple and very isolated component change. Even then, we're all almost certainly too aero-stupid to draw meaningful and correct conclusions from reading the tea leaves after the fact. The beauty of using strings is in their simplicity and stupidity - at least you see what's happening as it happens, rather than trying to deduce what happened from an end-state; you (the general "you", which includes me) are still more likely to be wrong than right, but at least you don't have a big mess to clean up.
03-04-2019, 08:52 PM
#19
Alright, I'll poke the bear. How so? Slather the radiator, do a run, and see how much ends up on the windshield? I think you picked perhaps the worst example in terms of making your point.
I can see some potential usefulness if you're comparing end plates for a wing, or some other very simple and very isolated component change. Even then, we're all almost certainly too aero-stupid to draw meaningful and correct conclusions from reading the tea leaves after the fact. The beauty of using strings is in their simplicity and stupidity - at least you see what's happening as it happens, rather than trying to deduce what happened from an end-state; you (the general "you", which includes me) are still more likely to be wrong than right, but at least you don't have a big mess to clean up.
I can see some potential usefulness if you're comparing end plates for a wing, or some other very simple and very isolated component change. Even then, we're all almost certainly too aero-stupid to draw meaningful and correct conclusions from reading the tea leaves after the fact. The beauty of using strings is in their simplicity and stupidity - at least you see what's happening as it happens, rather than trying to deduce what happened from an end-state; you (the general "you", which includes me) are still more likely to be wrong than right, but at least you don't have a big mess to clean up.
I would imagine a bit of it depends on the paint recipe:
Tempura paint powder (fluorescent if possible as it shows more detail under UV light), mineral spirits and a drop or two of oleic acid to keep the powder from coagulating.
Just the powder and engine oil will work acceptably. One also has a choice of whether to smear on the visualization paint and watch it move or drip on dots and watch them turn to lines or stop at separation lines or not move within separation zones. One has to beware of the effects of gravity on thinner liquids.
Using mineral spirits or kerosene as the solvent results in a picture that doesn't change when the vehicle (or the wind tunnel) stops. The solvent evaporates leaving the pigment stuck to the surface. One can see flow direction and, with some judgment, separation lines or zones. The fundamental is that the paint is moved by shear stress (at the surface) and shear stress goes to zero at a separation point. Hence the paint stops moving and puddles up at a separation line. Tufts also will show flow direction and will wave wildly in a separation zone. They don't show separation points/lines so clearly.
You can make flow vis solution out of almost anything really. I've even used a mix of brake cleaner, T Cut polish and monkey butt powder! It worked really well. The 'proper' recipe is the flourescent powder (which shows up really well in UV light), parafin (not sure what you guys call that over here) and a dash Oleic acid which acts as an anti coagulant. Slap it on the underside of a wing (or anywhere you like) and run the car (or wind tunnel). The parafin will evaporate leaving the powder to show you how bad your wing is stalling!
British "paraffin" is kerosene. The advantage of kerosene over oil in wind tunnel testing is that it eventually evaporates, leaving the pigment behind. Pictures can be taken after the fact with the tunnel off or the car stopped. One does have to worry about the effects of gravity on the paint in regions with low shear stress - does the paint follow the flow or run down because of gravity or is it a vector combination?
03-05-2019, 07:22 AM
#20
Registered User
You quoted me, so I feel obligated to reply ... but the only relevant comment I can make is that it's tempera, not tempura, unless we're talking about lunch. Not sure who asked for paint recipes (I'd have preferred tempura recipes, to be honest).