Originally Posted by
dera
Pretty much instantly. The pressure ratio drops to zero almost immediately, that's the woosh-sound you hear when a turbofan engine is shut down.
Yes. The fan slows to a negligible speed within moments. The fan is the danger... a lot of air volume at a fairly low diff pressure will apply a lot of force to a surface area of a a few square feet.
If a person's torso is approx 1'x3', that's 432 square inches... a one psi diff pressure will apply 432 lbs of force.
The N2 spool doesn't move much air volume in a high-bypass turbofan.