Quote:
Originally Posted by freebeard
Anybody have a guess what a 'diffuser' looks like?
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According to an earlier post by aerohead, a diffuser is an upward slanted surface which allows some recovery of pressure at the rear. This minimizes wake behind the vehicle. As the OP stated, such a section might take a curved shape, like the rear of an inverse airfoil.
Hucho provides two examples of flat single plane diffusers in figure 4.48 of his "Aerodynamics of Road Vehicles." In example one, where the diffuser length/car length= .326 (i.e. a rather long diffuser) the diffuser works best at about 2.6-2.8 degrees upsweep and provided a Cd reduction of something more than .025. The second example, the ratio is .178(i.e. a rather short diffuser), the diffuser worked best at about 4 degrees upsweep and provided a Cd improvement of about .020. These are small improvements, but significant when added to other aero improvements.
In practice, one would fabricate these diffusers with flat sections of metal or coroplast. Look earlier in this thread and you will see examples on my Insight. If you study the pictures you will see that there is a clear angular break between the forward underbelly and the rear diffuser section. The diffuser is at about 3 degrees, not perfect, but close.
Later: Sorry, check post 17 in this thread:
http://ecomodder.com/forum/showthrea...s-22691-2.html