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Old 12-28-2009, 06:57 AM   #1 (permalink)
Rokeby
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100% Bluff Body Drag Reduction Theory

This may be the Holy Grail of auto aerodynamics.
Unfortunately, like the Grail, it may be unrealizable for mere men.

From time to time, posters ask why hasn't anyone come up with a way
to reduce a vehicle's drag similar to the bulbous bow that is used to
reduce/cancel the bow wave on large ocean-going ships.

Well, I stumbled on this presentation which shows at least a theoretically
possible way to do it. I'm skeptical. This appears to be too good to be true
-- or at least too impractical to implement -- but it is also too good not to
share.
First the pictures, extracted from a PDF:

Click image for larger version

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Click image for larger version

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Well, there it is in all it's impractical glory; 100% bluff body drag reduction.
Things aren't perfect though, the plate-bluff body system reduction is only
62%

If your vehicle is 50 inches wide, all you need do is have a vertical plate
~18 inches wide held in place 75 inches in front of the vehicle.

Simple? Yes. Practical? No. Nonetheless, it would be interesting to see if it
worked in real life. I suspect that even a small crosswind component would
greatly diminish or wholly negate any benefit.

All of this from:

Bluff Body Aerodynamics, Lecture Notes by Guido Buresti.
Department of Aerospace Engineering, University of Pisa, Italy.
6.12-16.2000; Pages 28, 29.


Last edited by Rokeby; 01-04-2010 at 09:58 AM..
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