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Old 1st Jan 2011, 21:56
  #57 (permalink)  
Join Date: Sep 2000
Location: Bielefeld, Germany
Posts: 955
Terms such as "ram drag" and "inlet drag" are by no means ubiquitous. This may account for why so many people do not know what they mean. And they sure don't occur in textbooks such as Anderson's. If they don't occur in textbooks, it is surely not surprising that many people don't know what they mean.

Definitions would be helpful. Or references to them in publicly-available sources.

In particular because, if one does look in textbooks, such as John D. Anderson's Introduction to Flight (which is ubiquitous), one will find (courtesy of Rolls-Royce PLC) in Figure 9.19, p720, a division of the x-axis components produced by a jet engine in normal thrust-producing mode: in sequence from front to back,

Compressor produces about 19,049 lb forward
Diffuser produces 2186 lb forward
Combustion chamber produces 34,182 lb forward
Turbine produces 41,091 lb rearward
Exhaust unit/nozzle produces 5587 lb rearward

It should be obvious with a little thought that this situation can only happen when gas is passing through, not when gas is stopped and diverted perpendicularly. So using the same terminology for what happens in the two cases is somewhat apples-and-oranges, I feel.

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