Random Wind Tunnel and Smoke Pictures Thread

[freebeard]

http://www.youtube.com/watch?v=LtXOUrTc_dA

[CFECO]

Cool, I'd like to see it going backwards. The A-2 wind tunnel Bug in both directions was interesting, but the raised hood messed up the flow from the rear some, and we didn't see the rear of the car with the smoke wand held at the rear window-hood area, with the wind from the front.

[kach22i]

Much more air going off to the sides of the greenhouse/canopy than I would have imagined.

Although this is a CFD model, might we consider that those arrows might not be representative of mass air flow?

The arrows might be only indication a path, or of a flow, and not any sort of volume indicator, right?

[CFECO]

In the wind tunnel scene of the 43 car, only a very small portion of the air hitting the front of the hood line actually goes over the roof. About 3/4 of it goes around the sides at window level.

[kach22i]

Originally Posted by CFECO

In the wind tunnel scene of the 43 car, only a very small portion of the air hitting the front of the hood line actually goes over the roof. About 3/4 of it goes around the sides at window level.

Maybe we should be paying much more attention to the greenhouse/canopy in plan then?

http://history.nasa.gov/SP-4103/app-e.htm

So versatile and practical is the wind tunnel that it is called upon for all kinds of research tasks. Above, a mockup of the Vought-Sikorsky V-173, set up in Langley s full-scale wind tunnel in 1941. Below, a submarine model mounted in the same tunnel in the 1950s; since air and water have comparable flow characteristics, a boat's performance under water could be predicted in such tests. (LaRC)

http://www.compositesworld.com/artic...things-to-come


http://www.autoevolution.com/news/au...ars-23250.html


Michigan Begs for $100,000 Engineers After Auto Rebound
By Jeff Green and Mark Clothier August 15, 2012
http://www.businessweek.com/news/201...r-auto-rebound

[kach22i]

Langley Research Center
Langley Research Center - Wikipedia, the free encyclopedia

Full scale model of the X-43 plane in Langley's 8-foot (2 m), high temperature wind tunnel.

http://www.uwal.org/uwalinfo/history.htm

During the early 1930’s, Fred Kirsten was eager to test his “Cycloplane,” his cycloidal propeller aircraft concept.

[aerohead]

Originally Posted by NeilBlanchard

It is a "useful" video, but one wonders about the narrowness of the wind tunnel? I thought the proportions of the tunnel had to be significantly larger than the car to be "true"?

The consensus seems to recommend that the test vehicle constitute no more than 5% of the test section cross-sectional area.Only a few tunnels qualify under this criteria.
Hucho does mention that the Pininfarina tunnel,while quite small in comparison,does produce numbers within the 2.5% standard deviation,which is right in there with the big league.
A2 may have some things figured out.Don't know.

[aerohead]

Originally Posted by Cd

I wish they would have shown more around the wheels and the underside, since this was the worst area on this car.

I emailed the guy that built this car. No Cd figures were given in the video, so I asked him if he would provide that data for us ( I also asked if he had data on the stock ( as in unmodified ) 'stock' car in regards to its' Cd and lift figures.

The site hasn't been updated in a few years so we shall see if we get a response.

Cali98Civic : I'm parroting what I have read regarding those scoops. Supposedly, those scoops were a last minute solution when the tires began rubbing the fenders above 200 mph. The engineers had some scoops from a SuperBee and attached them to the tops of the fenders backwards to hide a large hole that they added above the wheel "to exit some of the trapped air in the wheelwell." The front end of the car was so planted to the ground at speed that it was reducing the clearance between the tires and the fender.

Why the scoops face backwards is a guess to me. I had read it was to relieve the high pressure air in the wheelwell . It could just be a last minute solution to covering an ugly hole in the fenders, but from what i have read, they had some aero function.

EDIT : I emailed the guy with the car and he has replied that the testing was only done for stability and that no data was given such as Cd or lift.
( How does one pay $ 2,000 an hour and not get info like this ? ) :-/

The original 1970 Charger Daytona/Plymouth Superbird were reported by Marcell and Romberg at Cd 0.294 with the complete 'Daytona Package.'
They don't spell it out,but with a photo-enlargement of their published drag tables you can get it with linear interpolation.
*Without the nose and wing and other tweeks,the Cd is 0.35.
*The wing package added 7% drag at zero-yaw,and up to a 36% drag increase at 15-degrees yaw.
*Without the wing,the car was Cd 0.274.
*CAR and DRIVER reported a frontal area of 21.8 sq-ft,giving a drag factor,CdA= 6.409 sq-ft for the complete car.
*CdA 5.973 sq-ft without the wing.
*The underbody flow was significantly diminished with the front spoiler,and lift was reduced 66% compared to the 1969 'RACE' Charger.
*The wheels would have been real dirty.

[Thenorm]

not quite a wind tunnel, but an interesting aero effect as seen from space.
Isla Socorro creates von Karman vortices in the clouds above the Pacific ocean in this image captured by NASA’s Aqua satellite on May 22, 2013. (NASA).

[NeilBlanchard]

Originally Posted by aerohead

*CAR and DRIVER reported a frontal area of 21.8 sq-ft

That seems too low. The dimensions I find for the street version is 76.4" x 61.4" = 32.57sq ft minus ~15% = 27.68sq ft.