07-06-2009, 08:51 PM
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#1 (permalink)
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Ultimate Fail
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Book link ( PAC car )
Here is a link to some information on this ..um..... 'car'.
Supposedly at this time, it is the worlds most efficient road vehicle.
The World's Most Fuel Efficient ... - Google Books
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 Today
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Other popular topics in this forum...
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07-06-2009, 08:58 PM
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#2 (permalink)
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Ultimate Fail
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Adding ( tiny ) mirrors to the outside of the car increased the drag by over 50 % !
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07-06-2009, 09:51 PM
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#3 (permalink)
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Pokémoderator
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Cd -
Great find! I dig that car/trike/human torpedo ?!?!?!
CarloSW2
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07-06-2009, 10:00 PM
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#4 (permalink)
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Batman Junior
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07-06-2009, 10:10 PM
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#5 (permalink)
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Batman Junior
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Scanning the book, I learned something new.
Background: they were attempting to retain a laminar boundary layer as far as possible down the body.
One method they used to detect transitions in the boundary layer was by usng a stethoscope probe that kind of looks like a pitot tube! See fig 5-35, p 123.
And because they were able to achieve laminar flow, "the friction forces dominate the pressure forces" - the opposite of most road vehicles (p. 127).
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09-19-2009, 04:10 PM
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#6 (permalink)
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Master EcoModder
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Disingenous?
I've been mulling this article over in my head ever since it was posted.The claim of Cd 0.075 is truly remarkable and I've struggled with the context ever since.------------ The premise of the design was to keep the Reynolds Number below critical,remaining in a laminar flow regime for the entirety of the competition.That's all fine and well for a closed-course academic exercise but it has little bearing on the real world.No doubt, 7,000 mpg sounds appealing and it is a fact that these numbers are being generated,it's just that it doesn't dovetail into the "real" world very well.-------------- When Subaru and GM got Cd 0.088 in the wind tunnel,their vehicles were at or above critical Reynolds Number and reflect drag numbers that could be expected in the "real" world,at "real" driving speeds.---------------- I don't mean to marginalize the effort that went into the PAC car,it's just that for me,when these numbers are tossed around,there might be special emphasis added to remind the reader of the context in which these quanta are registered,and should an architecture like PAC car be scaled up and operated at typical road speeds,then the operator might expect diminished performance.Just opining.
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