David Lednicer wrote:

Dave, what is the max rate of change of cross sectional
area of an axi symetrical cooling duct with a radiator
at the end. We are trying to squeeze these things into
Lancairs and RV's

        Instead of approaching it on this basis, you really need to see
what shape should be used and why.  I recommend finding a copy of
Kuchemann & Weber's book "The Aerodynamics Of Propulsion".  In Chapter 12,
they have a long discussion on cooling, centered on inlets and outlets for
radiators.  Section 12-3 (page 274-278) is specifically on diffusers and
they present coordinates for a streamline diffuser, which is the optimal
shape to use.  

-------------------------------------------------------------------
David Lednicer             | "Applied Computational Fluid Dynamics"
Analytical Methods, Inc.   |   email:   dave@amiwest.com
2133 152nd Ave NE          |   tel:     (425) 643-9090
Redmond, WA  98052  USA    |   fax:     (425) 746-1299

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