How does the bypass region of a turbofan work? I understand that some of the air enters the engine core while much of it is routed around the core (bypass). How does this re-routed air produce so much thrust? Also, what's the definition of "high" bypass? I've heard a 4:1 bypass ratio.
What compressors/turbines are identified as N1, N2, N3? (N3 is only applicable to RR engines, correct?) Finally, are there any good websites that explain engine operation? Thanks.