Mailing List flyrotary@lancaironline.net Message #4953
From: Tracy Crook <lors01@msn.com>
Subject: Re: [FlyRotary] Re: Streamline Vs Parabolic Ducts/Diffusers
Date: Wed, 24 Dec 2003 16:57:50 -0500
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
 
Reply #2..      
  Ed,  Are you sure the labels are not backwards on the two duct pressure recovery charts?
 
Tracy
 
 Labels are correct, however, I used two different Y scales for the dynamic pressure on the two charts.  The dynamic pressure values are correct but the unequal scales appear to give the parabolic curve the greater dynamic pressure recovery, when in reality it is the streamline duct.
The Y axis on the right is for dynamic pressure.
 
 
I just posted the two charts with their dynamic pressure scales equal and I think it is clearer now.
 
Ed Anderson
 
Ahh!  that explains it.  The only thing missing (for me) is that I don't have a mental picture of the streamline duct shape.  In fact, I may have it wrong for the parabolic as well.   I picture the duct area for the parabolic going up like the chart for the streamline shows it.
 
I also thought a 7 degree duct was a simple straight sided duct with sides that diverge at a 7 degree angle from the centerline.  Maybe I'm more confused than I though : -)
 
BTW, this is great stuff Ed, keep it coming!
Tracy
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