Question about kamm extensions.

[Christ]

Originally Posted by FastPlastic

What about strait out the back like the lamborghini has? It would be a little like looking through a venetian blind.

Same basic design, except there's a window behind those louvers. In the design I was asking about, the window extends away from the driver with the louvers.

EDIT: I'd buy that in a heartbeat.

[cfg83]

Christ -

Originally Posted by Christ

It seems like the larger steps made the oscillation of the wake slow down to a lower frequency... I didn't count frames to find out, but it looks that way at a glance... anyone verify this?

We have to be careful about what the flow simulator shows. It may mislead us or we (I) may enter the wrong defaults (garbage in, garbage out) and throw off the calculation. While it demonstrates *principles*, the author does not claim real-world results.

http://ecomodder.com/forum/showthrea...ator-3709.html

The author, Sergie, introduced himself on page 4, post #126 :

Originally Posted by Sergei

Hello everyone,

Thirdman told me about this forum and this thread. Naturally, I was happy to see the interest in Flow Illustrator, and also I noticed a lot of recent activity on the server, which is now explained.

I would be gratefull for your comments, as this may improve Flow Illustrator. If, say, the functionality of it is fixed, what can be improved?

Another thing: I read all the posts, and, rather naturally, the level of the background knowledge of aerodynamics and CFD (Computational Fluid Dynamics) issues, well, varies. I would be happy to explain things, but there is just no way to explain aerodynamics in one sitting, and it would be nice not to need to repeat the same explanations again and again. May be I should concentrate them somewhere. Would there be much interest, do you think, to something like 'Aero without math' blog (run by a professor of the Department of Aeronautics of the Imperial College London, which, as you surely know, is one of the best universities in the world :-))?

Question: Could we be looking at the origin of the "dropped tailgate" theory? I mean, maybe it does work for the few trucks that can drop their tailgate and get an 11-13 degree drop from the rear of the "cab roof" to the end of the opened tailgate.

CarloSW2

[Christ]

Carlos -

I see - I also figured as much, I just thought it was an interesting visual oddity, insofar as to notice it, but not attempt to actually verify it myself, rather asking if anyone else had seen it.

Kind of like asking "Whoa - did you see that?" Instead of just looking again.

Many thanks to the author of the program, though. I wasn't a member during that process, I think.

[aerohead]

Originally Posted by Christ

I was actually referring to a shape more like stairs, but keeping the upper edges of the 90* "steps" on the same 10-13* slope

So it would have several 2" "clear steps" that are vertical and appreciate in distance from the rear window, and have horizontal "slats" connecting them, which also appreciate in distance from the rear window, starting from top to bottom.

If I have to find a pic, I will.

Christ,I was looking through a Porsche book and they had a photo of the 917 racer which had a stepped Lexan cover over the mid-engine portion of roof.This is also the inlet for cooling air and the vertical portions are wide open.I believe this car had Cd 0.27 even with all the induced-drag downforce.

[Piwoslaw]

Originally Posted by FastPlastic

What about strait out the back like the lamborghini has? It would be a little like looking through a venetian blind.

Oh my, that Lambo not only has a step-kamm rear, but also a side mirror delete. Oh, and do I see aero-friendly dimples in the door?

[Christ]

aerohead -

I wonder if having the intake there helped any with keeping attached flow in the back? I can't really imagine the engine takes in that much air, but there might be something to the design with having the intake's vacuum only a small area above the exhaust's pressure to create a sort of bubble around the lower portion of the rear of the car that aids the flow by making a sort of "imaginary" boat tail extension?

It's a long shot, but I have to imagine that it's having some effect with such a low Cd on a high-downforce design.

[aerohead]

Originally Posted by Christ

aerohead -

I wonder if having the intake there helped any with keeping attached flow in the back? I can't really imagine the engine takes in that much air, but there might be something to the design with having the intake's vacuum only a small area above the exhaust's pressure to create a sort of bubble around the lower portion of the rear of the car that aids the flow by making a sort of "imaginary" boat tail extension?

It's a long shot, but I have to imagine that it's having some effect with such a low Cd on a high-downforce design.

Christ,the intake may have behaved as a low performance suction slot,helping to vacuum the boundary layer onto the roof.Hard to verify without the car.Porsche does have their own windtunnel and while 3rd-party modifications have crashed,Porsche's designs have faired well in competition and I bet they really sweated the details on the 917.