I've been searching the internet for awhile and haven't really come across a good answer for this question. So:
I have a basic understanding of the principles of flight (thrust, lift, drag, etc). But one thing that has been confusing me is how exactly a thrust reverser on a high-bypass turbofan engine works. So from what I understand, the large fans at the front of the engine will provide the majority of the thrust. Air coming through the inlet nozzle produces an action-reaction pair on the fan blades to produce this forward thrust. So upon deploying the thrust reversers, the air that has already produced a forward thrust on the fan blades now moves back through the bypass duct to strike the thrust reverser, thus redirecting the air forward by creating another action-reaction pair to slow the aircraft.
So it just kind of seems to me that the thrust reverser just cancels out the thrust from the fan blades. Or is the air coming off the fan blades is accelerated so that by the time it hits the thrust reverser the forward directed thrust is greater than the thrust generated from the fan blades, thus producing a net reverse thrust?
Or maybe I'm just looking at this wrong and need to think of the entire engine as a closed system so that the air pushed backward from the fan doesn't produce an action-reaction pair (and thus thrust) until it exits the engine?
I'm just kind of confused on the specifics of the physics of the thrust reverser (where the action-reaction acts).