On Wed, 11 Aug 2004 at 11:26:14 in message
, Todd Pattist
wrote:
So we have a blade hitting air that is 15" away from air
that was hit by another blade. The pressure disturbance
from the first blade propagated at the speed of sound over
that 15" and has arrived at the "new air" 15" ahead long
before the airplane and the second blade arrive , so there's
some effect there. I'm also not a prop designer, but you
need more to convince me than just saying they are 15"
apart.

Let us assume a cruise rpm of 120knots == 202 ft sec

Then assume cruise rpm is 2000rpm

@ 2000 rpm is 33 revs per second

advance per revolution = 202/33 or 6 feet.

So three blades would arrive at the same spot every 2 feet. I am not
sure that means much because we know the flow is rotated by the prop as
well.
--
David CL Francis