ORIGINAL: Lnewqban
Once leaving the rotating blade, what force would cause the stream of air rotate for long, if any rotation requires a centripetal acceleration?
There ain't one -
You don't need text books to proove this
simple observation will do-
remember - in nature everything tends to static and equal condition.
The higher pressures irrespective of momentum will -unless confined - simply reach the static or ambient conditions
Even the dreaded wing tip vortices -which DO exist - gradually "go away'
Nothing mysterious about it.