Racecar Eng. aero article compilation

[i3igpete]

http://www.rightwheeldrive.com/Aero_articles.zip

pretty cool series of articles, don't know if it's been posted on here before. Some interesting things I've found so far:

-double airfoil wings can be run with really steep secondary airfoil angles and still build downforce (v14n9)
-installing smooth underbody panels have a negligible effect on drag (v15n1)
-nascar-type spoilers are actually pretty effective (maybe someone should try this!) (v15n2, n3)
-splitter-to-ground clearance doesn't matter much at all for downforce, classical theory doesn't work due to high viscous effects (v14n5)

[BigTyla]

Damn it, why did you have to post this? You KNOW posting "aero" in any article is like a magnet drawing me in and forcing me to read the material!

Will have to read at lunch and try to provide some commentary.

[J. Fast]

This is my wing.
Bought it from some ebay guy who makes these in his spare time in China. It was $365 with the CF uprights. I picked it for the chord and never knew there was CFD info on it so... sweet! So much more downforce when you combine two different wings? I didn't really get the tradeoff portion of the two wing, I sort of rushed thru the articles since I didn't have much time. Was it increased drag with speed?

[Gearhead]

This is my wing.
Bought it from some ebay guy who makes these in his spare time in China. It was $365 with the CF uprights. I picked it for the chord and never knew there was CFD info on it so... sweet! So much more downforce when you combine two different wings? I didn't really get the tradeoff portion of the two wing, I sort of rushed thru the articles since I didn't have much time. Was it increased drag with speed?

Can you post a link to his ebay page? I like the look of it and after reading those articles, I want to get one.

[J. Fast]

Can you post a link to his ebay page? I like the look of it and after reading those articles, I want to get one.

His name is Carl Lan. He is a builder for Zuhai. Send him a message at his Tradeford Listing, Zhuhai Stone Carbon Co. Ltd, China
He also has all sorts of other carbon fiber wings and misc aero parts avail. Parts are functional and affordable

[J. Fast]

Another picture that was emailed from the builder It is 64" wide

[i3igpete]

there's really no trade off at all, a dual-element wing can run a ridiculous amount of camber that a single element will stall with. Consequently, he can probably jack up the angle on that second element without stalling it.

btw, is that a voltex knock-off?

[J. Fast]

btw, is that a voltex knock-off?

Yes it is. It's very similar to a Voltex GTPro-Type 3. It would be very difficult to discern one from the other unless you had the upgraded Voltex base supports. The basic base support mount on a voltex pretty much looks identical from what I could gather from the illustrations voltex has posted from their website: VOLTEX_GT WING

.

Edit: And it's also roughly $1700 cheaper than a voltex.

[BigTyla]

I have read the first four articles, but V14N5 (talking about underbody venturi tubes) really drew my attention. Some comments:

1) I can imagine that spillover effects would be significant in this problem. I'd really be interested in seeing some 3-D numbers but I understand the reason for staying 2-D here since 3-D is not only more complex but is also significantly more computationally expensive. I'm happy to see the author mention that steeper diffuser angles would be permitted by 3-D effects. He knows his stuff for sure!

2) Air speed at the inlet was never specified in the problem. This is a critical variable as it would seem ideal to design the venturi tube with the most frequent air speed in mind (or the situational speed at which maximum possible downforce is desired). A venturi designed specifically for the vehicle's top speed might end up operating terribly during cornering speeds. That leads me to question whether the flow within the venturi tube would ever be anything other than fully-developed turbulence, as a boundary layer in the process of transition will show significantly higher flow separation penalties at the diffuser than the fully-developed case. Of course this can be solved trivially by integrating vortex generators in the venturi design, deliberately tripping the flow to fully-developed turbulence.

3) Why not design the diffuser wall with camber to reduce flow separation penalties? Seems like a pretty obvious solution to me. It's not like cambering the diffuser is hard or expensive, particularly with sheet metal designs.

[i3igpete]

I have read the first four articles, but V14N5 (talking about underbody venturi tubes) really drew my attention. Some comments:

He does a bunch of 3D analyses later, but I was mainly intrigued how different reality was from Bernoulli. Very interesting how the downforce is almost constant, regardless of the clearance.