Cd 0.38
 

Just to illustrate some of the variability of shapes with identical Cd
http://i1271.photobucket.com/albums/...titled1_24.jpg
http://i1271.photobucket.com/albums/...d2/06-2826.jpg
http://i1271.photobucket.com/albums/...titled19_3.jpg
http://i1271.photobucket.com/albums/...titled1_19.jpg
http://i1271.photobucket.com/albums/...titled9_19.jpg
http://i1271.photobucket.com/albums/...titled8_19.jpg

I just don't understand.
How can the Smart car have the same Cd, yet have such a massive wake ?
The wake of the Z-28 is tiny in comparison.

Are the vortices just more controlled in that design, or what ?

Cd (a dimensionless number) is what's being asserted. But I'm wondering for an equal A (area) does the height/width ratio have any impact? The Template would be .5, my car closer to 1. The Smart could be over 1.

This is based on the sides having twice the taper of the top.

how can
 

*The car is highly detail optimized,with minimal turbulence before the tail truncation.
*It has extremely good sectional density,displacing the air nicely with it's leading edges for complete flow attachment,and gradual reduction in cross-section allowing separation-free flow to the truncation,with perfect pressure recovery.
*It's fineness ratio is adequate for Cd 0.38.
*While it DOES have a relatively large wake,the base pressure is higher due to the careful contours and pressure recovery upstream.Just like a 2015 Ford Econoline which shares the same Cd.
http://i1271.photobucket.com/albums/...titled9_15.jpg
*It's 'Stromform' nose is of the lowest drag.
http://i1271.photobucket.com/albums/...Untitled24.jpg
*It's the only car with a proper K-form truncation.
*It has zero-induced drag penalty.
*There is essentially zero vorticity.
*The base pressure of the Z-28's wake will be the same as at it's early separation point,way forward on the back slope.Very low pressure! Quite a penalty!

height/width
 

Kamm and Fachsenfeld tested this at the FKFS and the short answer is no,it didn't make a difference.
They varied the width of their airfoil-shaped model from around 230mm,to 1,000mm,holding the height constant,and recorded the same Cd, on a frontal area basis.
Any car of any scale will have an identical Cd as long as Reynolds number is accounted for.They call is dynamic similarity,or verisimilitude.
The tunnel velocity must be such that a turbulent boundary layer is guaranteed.

I had to look that one up.

http://ecomodder.com/forum/showthrea...orm-28260.html
I had the same reaction as "Cd", still amazed.

same reaction
 

Aero's a funny thing.So far,the best for cognitive dissonance is this comparison,both cars Cd 0.311
http://i1271.photobucket.com/albums/...titled10_1.jpg
http://i1271.photobucket.com/albums/...titled16_4.jpg
:D

thanks Phil. This all gives me hope that my Kamm efforts are the way to go.

But ...but ...it has a pointed nose. ;)

I agree. I still think a flat spoiler would look cooler, or at least strange in a striking way, but I bet you get better results with your Kamm ideas.

Kamm efforts
 

From Jaray's,Lay's,Kamm/Fachsenfeld's,Hucho's,and Buchheim et al's research,it's the only thing which has a track history of performance.
Darin's Honda proved that it's not a 100% solution though.I suspect that there was drag reduction,but the engine didn't react favorably to the mods.
Chrysler and Dr. Gino Sovran warned about gear-matching requirements.Hope you don't hit a snag.

More of that "entemodynamics" I have spoken of in the past. If the bugs don't stick it must be a good thing :D
I am kicking around a kamm with a big wing..... or two. fun fun!

My TDI's fuel specifics are so much better than a gasser, and I will be adding a 6th gear eventually. I don't imagine that being an issue, ever, at any speed.

I believe our diesels are less sensitive to throttle position changes due to the diesel engine's lack of a throttle plate. Improved aero should only help efficiency since they simply add less fuel with reduced load and can run very lean compared to a gasser. That said, if you can do the 6 speed swap and keep the engine at about 1,800 rpm at your chosen highway speed that is the sweet spot for BSFC for the TDI. It's on my wish list.

Back when I had the 1961 VW panel van, I thought about two Porsche duck tails, vertical on the sides, to create what I would verbalize today as a virtual plan taper.

More for directional stability than downforce, like a shuttlecock.

I had a similar thought last year or two ago when those air-tabs on the side of vans first came out. Although it would be just the common Wickerbill sized Gurney flap all the around the rear edge.

Once I'd hung around here for a while, I leaned more toward a rectangular 4" torus fed with the pumped engine cooling air, with louvers punched lengthways at the proper angle to form a Coanda nozzle on all four sides.

Today though, things are different. The news out of Manchester University:

The future of flight: plasma aircraft wings | News & Events | Manchester Metropolitan University

POSTED BACK IN 2011................four years ago.:cool:

Page 2
Why are many UFOs an aerodynamic, saucer shape?
Why are many UFOs an aerodynamic, saucer shape?, page 2
http://forums.pelicanparts.com/uploa...1446563860.jpg
http://forums.pelicanparts.com/uploa...1446563993.jpg

How long before our cars start glowing blue?

Puddle lights? we don' need no stinking puddle lights!

Purple? They've been preparing us since Tron, with the blue strip lights on everything.

I need plasma wings on my belly pan!
And spinner moon discs. ;)

I'm out of state, and writing on my NOok tablet; so this is painful, but Plasma Actuators.

Popular Science, November 2015, page 26.


=)

Edit: searching to find this thread, I see this has been discussed before.

In fact I was commenting on it in this thread last July. The memory is the first to go. Or is it the knees?

Anyway, here's a Wikipedia entry on Plasma Actuators