Aero photos from El Mirage SCTA finals

[California98Civic]

Just a handful of pics arranged in an order meant to help you see aero features. Several pics are of the dust trailing wakes of the cars I photographed before their runs.

Here is the wake of the streamliner motorcycle featured in the attached pics:


Here is the wake of a roadster:


Here is the wake of the yellow Austin van featured in the attached pics:


All images taken from almost the same distance, give or take a dozen yards or so...

[NachtRitter]

Great pics! Thanks for sharing. Any additional info on the vehicles in the pics?

[California98Civic]

Originally Posted by NachtRitter

Great pics! Thanks for sharing. Any additional info on the vehicles in the pics?

Oh yeah, some... that red and white ferguson streamliner has a Hondata engine in it. Earlierin the year it ran 243mph. On the run you see it getting pushed-out for ithit 229mph. That streamliner motorcycle was wicked fast and has been running for several years now, with a best of speed something in the area of 200mph, IIRC. The little white Chevy Spirit with the turbo is a fixture kf the SCTA events, driven by different drivers all the time. It's fastest ever was 117mph. On the run you see it starti g it ran 109mph. It's called "the peanut" on the track even though that nameseems nowhere on the car. The yellow Austin has a Bonneville type spoiler on the back, but it is just to keep dust off the rear windshield at the insistance of the driver, go figure. It can't be helping aero at that size and position, can it? The motorcycle was just too cool to pass up. The rider was awesome. Speed snifting with perfect effectiveness. Forgot to listen for its top speed report. And that last car is my Civic, photographed as the yellow Austin raced by. Was a great day.

[kach22i]

I love the detail shots like this one.

[renault_megane_dci]

Can't really tell much from the dust wake if vehicles speed is not consistant, can we ?

[wmjinman]

Originally Posted by renault_megane_dci

Can't really tell much from the dust wake if vehicles speed is not consistant, can we ?

That, and also I suspect it has as much or more to do with weight than turbulent aero wake (the amount of dust the wheels pulverize underneath them). At the Black Rock Desert, a big truck kicks up a dust trail many times larger than a car. - of course, I guess it probably has a bigger turbulent aero wake behind it, too - - - -

[California98Civic]

Originally Posted by wmjinman

At the Black Rock Desert, a big truck kicks up a dust trail many times larger than a car. - of course, I guess it probably has a bigger turbulent aero wake behind it, too - - - -

This size of the vehicle as i understand it is closely related to its total drag, in as much as CdA is a calculation of Cd and frontal area. I took these photos partly because aerohead once suggested in a thread hee on EM that a lot can be seen in the dust trails formed behind vehicles at El Mirage. You can't read it for numbers, like the Cd or lift or whatever. But you can plainly see the scale of the wake left y that sleek, small, streamliner motorcycle versus that yellow Austin. It's a flow dramatization, not a measurement. But the dramatization is useful too.

[wmjinman]

Right.

And for the weight thing, I guess the test would be to drive a fully loaded semi and an unloaded one side by side & compare their dust trails. I guess I'm also thinking about the tracks they leave in the dirt..... those big duals plow up a lot of dirt when they roll over it with all that weight. To me, that has to translate to much more dust in the wake.

Compare it to a motorcycle going the same speed, maybe. Of course, you'll say the motorcycle has a fraction of the frontal area, too..... Hmmmm - - can we somehow load 10 tons onto a motorcycle????? or reduce the weight of said semi truck to 1000 lbs???? Maybe a strict weight vs. frontal area test would be difficult.....

[aerohead]

The photos are great!
If wind tunnels had test sections this long and you could photograph the test vehicle at a far enough distance we'd see the same thing if smoke was introduced into the wake.
This illustrates the magnitude of the wake and its relationship to fuel economy,and how an internal combustion 1987 Sunraycer would achieve 300 mpg.
Hucho could use these sorts of images in his books.
Thanks mucho! I would have liked to have been there.

[aerohead]

Originally Posted by renault_megane_dci

Can't really tell much from the dust wake if vehicles speed is not consistant, can we ?

The drag coefficient becomes constant at around 20-mph.So the wake behavior would also be constant up to about 250 mph where compressibility effects come into play.
The magnitude of the energy is following the square/cube relationship,so sure,the wake will be more dramatic if a Bugatti Veyron or Mike Cook's Thunderbird blows by at over 260 mph.
The lake bed dust is already pulverized.And sure,if you've seen video of the Lunar Rover you know that the tires will sling dust even in a vacuum.But it is the low base pressure of the turbulent wake which allows the dust to migrate far afield of the tires 'toss' area.
Ritchie Ginther's first rear spoiler was designed to prevent this 'dust' from moving forward into the cockpit of his Ferrari and killing him.It was only an accident that it also spoiled rear lift.