Originally Posted by PBL
ChitterneFlyer, this isn't about semantics.
PBL,
Please forgive me if I start my reply with your last remark. I was about to reply exactly the same but, after carefully re-reading your post #50 of Januar 1st, I must agree with ChitterneFlyer that the discussion is to a large part about semantics. What you call "momentum reduction (...) experienced as a braking force" is what I would call "intake momentum drag", and others "ram drag". The term "inlet drag" is somewhat ambiguous, because it could refer to the skin friction or pressure forces acting on the intake duct.
That brings me to the forces 'produced' by engine internal components that you quote from J.D. Anderson's book. Without an explanation of how they are derived, these figures don't mean anything to me. I suspect they have to do with the structural design of the engine carcass, loads on bearings (see discussion on QF32 threads), etc., but they don't seem particularly relevant in the context of engine performance.
Now that we agree on the intake side, let's turn to the exhaust side of the engine, which to me seems to be slightly 'under-exposed' in your account. For a given engine and flight condition, the inlet mass flow (the mass of the air that enters the engine intake) is, as you say, a function of engine RPM. In principle, that relation is the same for forward and reverse thrust regimes, except that deployment of the thrust reversers may result in a change of the effective final nozzle area, and thereby affect the internal 'matching' of engine components.
In other words, for a given RPM, deployment of the reversers doesn't change very much on the intake side, but affects mostly the 'nozzle thrust' by varying degrees of effectiveness, depending on the design of the reversers. In addition, as pointed out by others, the 'reversed' exhaust plume can have adverse effects on the aerodynamics of wing and control surfaces, and can be re-ingested by the engine. Due to these adverse effects, reverse thrust usually needs to be cancelled or reduced at low speed, which adds to the perception of ineffectiveness at low speed.
regards,
HN39