Help to understand these two images
 

Hi all!

I've been reading successful cases in Fluent web site about external aerodynamics developements in the shape of cars to reduce the drag. Particulary, I read about the Eco-Roadster by Opel and an Opel Astra and in both texts it is showed a plot of an iso-surface of ptot=0 coloured by turbulent kinethic energy (TKE) that I don't understand very well:

Eco-Roadster: http://img83.imageshack.us/img83/903...oadster0dm.jpg

Opel Astra: http://img90.imageshack.us/img90/1708/astra8rr.jpg

The Eco-Roadster text tells that this plot helped the engineers to see where and how to make aerodynamic improvements to the shape of the car; the fact is that I'm not able to explain to myself how the iso-surface of ptot=0 coloured by the TKE could help me to realize where and how to make aero improvements. Why ptot=0 and not static pressure=0 or any other? And what has to do here the TKE coloured on the iso-surface of ptot=0? Perhaps the question is how interact TKE in the total pressure to make an increase of drag?

As you can see in the Opel Astra image, it is showed again that this particular plot seems to be helpful to engineers to make areo improvements in the final styling shape of their cars. Anybody could enlighten me with this a bit?

Thanks a lot!

Regards, Freeman