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Old 02-21-2011, 04:48 PM   #214 (permalink)
EcoModding Lurker
Join Date: Jan 2011
Location: Texas
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I am late to this discussion so please forgive me if I overlap some things.

There are several things that would be interesting to run through the CFD program. Number on would be an undertray and rear diffuser to a baseline model to see what difference it makes and then to the optimized upper surface model.

My observation about the use of vortex generators on aircraft is that they are positioned at a point near to or slightly forward of the point on a wing where laminar flow separates. The diagram I saw in the thread had them positioned too far aft I think. See what the CFD program says moving them forward incrementally until an optimal position is achieved. They can be added on to the actual car and tufts of yarn used to visualize the flow to see how well the full size model (the real car) compares to the CFD model.

I suspect that side fences along the fender line would have a larger than commonly expected effect upon the quality of the airflow along the sides of the car as well as allowing some potentially simpler mods to deal with the airflow over the top of the roof.

The shelf style 'spoiler' has been used in a number of applications which suggest that it might be worth exploring as a shorter (and therefore street legal) modification to a car than an extended boat tail or kamm tail which obscures the existing tail lights.

Additionally, it would be interesting to see what the computer has to say about modifying the airflow at the front of the vehicle with a 'bug deflector'. The reason they work to keep bugs off the windshield is that they deflect the airflow up over the main area of the windshield that the driver looks through. Obviously there may be some drag issues, but it could be interesting.

As to the Kamm back, the Cobra Daytona Coupe is an interesting example which was designed more by intuition than anything else and tested by shooting movie footage of yarn tufts placed all over it. Ultimately, a fairly simple spoiler was added at the rear to balance the car without much testing due to time constraints. You may also recall that the profile of the roof had the highest point farther aft than was or is today common to delay separation of laminar flow.

It should also be noted that the addition of a long tail could adversely affect vehicle stability in cross winds due to the movement of the center of lateral pressure to the rear. This should probably be run through the computer as well before beginning prototype construction.

This is a very interesting project you have undertaken and I am anxious to see how it develops.


Last edited by Pendragon; 02-21-2011 at 04:49 PM.. Reason: typo
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