An awful lot of guff, Guppy, but I think you made my point for me quite well.
You introduced the term "inlet drag" and said it was the phenomenon responsible for most of the braking effect of reverse thrust.
So I wondered what you meant by the term "inlet drag". (You may presume I had tried to find out!) I still don't know! And you still haven't said!
The point is that you used a concept in notes 13,
http://www.pprune.org/tech-log/43758...ml#post6141941 and 31
http://www.pprune.org/tech-log/43758...ml#post6151425 with (to me) some degree of confidence to "explain" a phenomenon (braking under reverse thrust), but apparently you cannot tell us what the concept means. That makes your "explanation" moot.
(I say "confident" because of the following exchange:
Originally Posted by mustafagander
Thank you Guppy. Please explain.
Originally Posted by Guppy
I already did. Read.
Which led me to wonder "he did?")
You hint you're not a mathematician, but the very first reference you cite is full of equations. Can we presume, then, that you are not actually familiar with the material in that reference? If so, I am at a loss to imagine why you cited it. (As I noted, it doesn't use the term "inlet drag").
AFAIK, the only place in internet-accessible documentation in which the term "inlet drag" is used is in the comments from 2001 on the sci.space.shuttle newsgroup by Henry (btw, both Henry and Mary are correspondents of mine from the '80's and 90's, although I haven't heard from either of them for a long time), and in a Master's thesis at the Naval Postgraduate School in which the term is also not defined. BTW, it's ironic that a term such as "inlet drag" should occur of all things on a shuttle newsgroup, because of course the shuttle, being driven by a rocket engine, has no inlet, and therefore no "inlet drag" (whatever that may mean)!
A term it seems you now want to use is "ram drag":
Originally Posted by Guppy
Mass airflow times TAS, subtracted from mass airflow times exhaust velocity, and there's your ram drag.
Is that the same as "inlet drag"?
I agree with what I take to be your point, that the braking force attibutable to use of reverse thrust is the force generated by taking all that momentum and stopping it in the x-direction, indeed I said so in my post 50
http://www.pprune.org/tech-log/43758...ml#post6153587. But my formulation is preferable to yours, because you mix up your units [Edit: too quickly said: maybe not. See HN39's post below!]
Just as a point on discussion etiquette, I don't think it's helpful to use lots of technical vocabulary, of which it seems you may not know the meaning, and link them with lots of qualitative math (such as "mass airflow times TAS") which it seems you also do not quite master. Wouldn't it have been easier to say you really just meant what I wrote in my note cited above? Then we'd all agree with you!
PBL