Pelican Parts Forums - Poor Man's Ground Effects -- I need some input

Pelican Parts Forums (http://forums.pelicanparts.com/)

- Porsche 911 Technical Forum (http://forums.pelicanparts.com/porsche-911-technical-forum/)

- - Poor Man's Ground Effects -- I need some input (http://forums.pelicanparts.com/porsche-911-technical-forum/182467-poor-mans-ground-effects-i-need-some-input.html)

What's the function of the 'side curls' on each corner of the front? It's a popular part of 993 fiberglass kits.

For the very same reason endplates are used on spoilers. It prevents the boundary layer air from simply rolling around the car. They force the air to stop at a certain point and move along the side of the car in a more uniform manner. Most of the time the lower spoiler section will rise upwards along the length of the "fence".

Yellowbird, did those pics come from the Kinesis website? That car looks vaguely familiar.

Jack,

To elaborate on Porschekid962's accurate analysis, we use a similar design on our splitter. If the goal of said splitter is to create some downforce at the front, those vertical "end plates" force the air to remain on the splitter slightly longer, instead of spilling off to each side.
(More drag - more downforce.)

The horizontal parts of ours are angled up toward the rear at ~ 10 degrees, becoming dive planes. If anyone ever doubts the effects of SMALL aero changes, implement something like this, and then alter their angles, say from 40 degrees inclination to 5 degrees. To an experienced driver, it is like a different car!

Ed LoPresti

Porschekid, Yes they are from the kinesis WS, I was looking for a new set of wheels and found the box rockers and front splitter and think JO need to see it.

winglets, vortexes, and bears. Oh my!

Quote:

Originally posted by JackOlsen
What's the function of the 'side curls' on each corner of the front? It's a popular part of 993 fiberglass kits.

Because of this thread I've been noticing that most 911 front air dams are lower in the middle and curve up at the sides. This would allow you to get as low as possible without dragging the corners while... cornering. The splitter, or the horizontal piece, would prevent lots of air from rolling off the dam and spilling under the dam. They also serve the purpose of preventing the air that is now flowing along the dam from rolling under the car. Finally any time you have something like a wing tip the air flow over the tip will form a drag inducing vortex that is proportional in size to the length of the wing. That is why air planes and F1 cars have the the winglets on the ends of the wings. The vortex off the large wing surface is blocked by the winglet and the vortexes off the winglets are much smaller. In the case of the front air dam with the folded up corners, without them the vortex might be directing spilled air under the car and generating drag. The vertical winglets also aim the vortex to flow over the roatating wheels which might even reduce drag from the wheels.

I wonder if the addition of skirts and dams would eliminate the need for the underbody tray? If there isn't much air under there to begin with, smoothing out the bottom might not matter as much. How much does it weigh?

Of course I may be completely wrong. I am remembering by aerodynamics class from 10 years ago, and those memories have been dragged through the mud of time and brain cell abuse.

banjomike's explanation of parastic vortices shed to the sides is what I have seen (and not on the Internet, either). They may serve multiple purposes. Only some serious testing can tell you what is the dominant effect.

I found a basic STL model of an SC on the web and thought it would be fun to do a quick flow analysis on it, given all the discussion in this thread. Unfortunately, the bottom of it is completely flat (Tyson would love it ;)), as I haven't taken the time to develop an accurate representation of the undercarriage. I also didn't put a "road" in the simulation, so the car is essentially floating in space in the analysis you see. If I have time, I'll make some changes and add "a road".

Nevertheless, it's interesting to see the low pressure areas (color coded, per the legend on the top left) and what not. As previously mentioned, the underside won't be very accurate since it's completely flat, and there is no road.

http://forums.pelicanparts.com/uploa...1100790968.jpg

http://forums.pelicanparts.com/uploa...1100790978.jpg

http://forums.pelicanparts.com/uploa...1100790986.jpg

What S/W are you using for this?

SolidWorks 2005 with CosmosFloWorks

Add vortices from the rotating wheels.....