Message-Id: <5.1.0.14.2.20031224130322.0361f048@pop.grc.nasa.gov>
Date: Wed, 24 Dec 2003 13:04:32 -0500
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
From: Joseph Berki <joseph.berki@grc.nasa.gov>
Subject: Re: [FlyRotary] Streamline Vs Parabolic Ducts/Diffusers
In-Reply-To: <list-2904083@logan.com>
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Ed,
         Is the parabolic duct the same as a 7 degree expanding duct?

Joe Berki

At 12:36 PM 12/24/2003 -0500, you wrote:
>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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