Re: Drag

["Rich Wagner" <drsavage@xxxxxxxxxxxx>]

John wrote:

>One sees both Cd and Cx. I assume they are the same, but perhaps not. Rich
>Wagner will know the etymology-

Aye, and there you've hit upon a raw nerve with us Aerospace Engineers. 
We've been using non-dimensional coefficients like these for ages, since
before the days of Reynolds and Prandtl.  They're a valuable construct that
allows us to relate and manipulate a myriad of factors which would prove
otherwise unwieldy.  As such, there are a myriad of non-dimensional
coefficients, and we are VERY careful to pick proper names when using them.
 In the case of Cd, we're referring to a force coefficient (as opposed to a
moment coefficient) which represents drag.  Easy enough.  Automotive
Engineers often develop their own terminology which uses different and
unfortunately, less descriptive names.  Without the actual test papers in
hand, I can't tell you what the "x" means with any degree of certainty.  My
assumption is that "x" refers to the force along the x body axis, which is
more properly deemed "drag".  So, in this case, Cd and Cx mean the same
thing.


Rich
Montrose, CO
'82 GTV6 Balocco

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