----- Original Message -----

From: Ed Anderson

Sent: Wednesday, December 24, 2003 12:39 PM

To: Rotary motors in aircraft

Subject: [FlyRotary] Streamline Vs Parabolic Ducts/Diffusers

 

For those of you interested in such stuff.  Attached is a gif of how
different ducts affect the conversion of kinetic energy in the airflow  to
dynamic
pressure.  It appears that the streamline duct's unique curve controls the
growth in diffuser area such that the non-linear growth in area (blue curve)
causes the  dynamic pressure recovery to follow a linear curve (yellow line)
and that is the key to the more effective pressure recovery of dynamic
pressure .  The parabolic duct curve on the other hand results in an
apparent linear growth in diffuser area which apparently forces the pressure
recovery to under go a non-linear development which possibly accounts
for more loss.  Not certain I understand exactly why, but it appears to have
to do with the difference in changing velocity of the air molecules near the
duct wall, boundary layers, separation and wall friction between the two
type diffusers.

Any aerodynamic types out there with a different interpretation?

Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
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