Quote:
Originally Posted by lunarhighway
maybe they mean Cd?
there's an interesting bit about the rear spoiler, where the first version is straight and the second seems to have something which reminds me of a gurney flap.
i've seen certain BMW's wich also have a small gurney flap like spoiler added. and quite a number of cars with a slight upward sweep to the rear spoiler lip.
given it's shown in this video i wonder what it's use is and how it works to aid FE. it would be a relative simple and good looking addition to my car, but i'd like to understand better what it's supposed to do.
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A big feature like a trunk-mounted spoiler may build up pressure ahead of itself to prevent separation on a back window. However, the small lips that sharpen trailing edges are intended to gather the existing boundary layer and trip it into the trailing vortex in an organized fashion, so that there are fewer sub-eddies. It is better to have one or two large, stable circulation patterns in a "trapped vortex" than just chaotic flow.