Old 28th Jul 2010, 12:13
  #88 (permalink)  
PBL
 
Join Date: Sep 2000
Location: Bielefeld, Germany
Posts: 955
While the English and their former colonists have persisted with the adaptation of a mercantile system of units to science, I am not at all in accord with the suggestion to
Originally Posted by john_tullamarine
confuse them all with slugs, poundals, ergs, and such like
because I hold it unseemly to berate the slug, poor creature. It is a necessary part of a system of consistent units.

I myself prefer the units which Mother Nature intended, in which the speed of light is 3 x 10^9, gravity is 10, the speed of sound in dry air at 15 is a third of a thousand, and, most quaintly, the Newton is about half an apple. But I do grant privileged status to the nautical mile as a minute of great-circle arc.

The point made by JT, that the essential coefficients of lift, drag, and moment are strict functions of AoA, Mach number, and Reynolds number, along with the derivation, is elegantly expressed in almost exactly those terms in Section 5.3, pp 262-8, of John D Anderson Jr., Introduction to Flight, Sixth Edition, McGraw-Hill 2008.

I tried summarising what I think are the important, sometimes revealing, points in this discussion, but it's up to about 4 pp so far, so rather than post it here I'll clean it up a little and likely post it on our blog, and publish a link here when I do.

PBL

Last edited by PBL; 28th Jul 2010 at 12:35.
PBL is offline