Try this, courtesy o' Streets.

http://www.clubhotrod.com/showthread...ght=volumetric

This one is BBB's that is phase 2

Here ya go Rick, and anyone else that's interested. An alternate term for what Richard correctly describes is Laminar Flow. The link talks about fluids, but you need to keep in mind that air, including exhaust gases, act as a fluid. As the link info suggests, flow at the wall is 0. http://hyperphysics.phy-astr.gsu.edu/hbase/pfric.html
I am sure they won't mind, will ya boy's? It's just such good stuff I couldn't let it slip bye.