Weather is actually a good example. It is definately free stream yet the centre of a hurricane is not moving and is at low pressure.
I just had a discussion with another chap who has fluid dynamics experience (dredging ships, so slightly larger than helicopters). The conclusion we reached is that directly below the rotor at ground level you would expect an increase in static pressure (due to change of direction of dynamic pressure), but further out you would expect a decrease as venturi effect took over. Certainly i would expect this on the ground, but i'm still amazed that the air itself actually compresses under the rotor.
Originally Posted by Shawn Coyle
Probably too much flight time at my disposal without definite things to do.... so I can pay attention to trivia....
Lucky so&so! C&C is an enjoyable read BTW.