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Old 11-26-2013, 09:24 PM   #43 (permalink)
Otto
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Quote:
Originally Posted by aerohead View Post
I believe that in the bar graphs,you see that after the very small radii were introduced to the 'basic' profile,that VW essentially achieved (within spitting distance) the same drag reduction as with the 'ideal' nose.
This is the concept of detail optimization that Hucho has hammered away at for decades.And why he is so quick to encourage the aft-body streamlining.
The forebody is in the most favorable pressure gradient,with the flow held against the body as it accelerates along the increasing body section towards the minimum pressure line.
You can have a lot of sins up front and still maintain attachment.
Granted, the airflow may stay attached on the upslope even if the entry shape is not so smooth, but per Hucho's page 158 graphics, the "optimum" nose looks a lot like that of the early Porsches, i.e., smooth, well radiused curve, with stagnation point set at ~20% of vehicle height.

I doubt we get much attachment with cars, especially after the airflow turns the front corners. A sailpane, otoh, can stay attached all the way to and sometimes beyond the thickest point of the fuselage, assuming excellent contour and surface quality. Not gonna happen with road vehicles.

I'm also curious about optimum shape of the nose as seen in planform, i.e., from above. Seems to me the lateral airflow would be best with an elliptical planform, smooth surfaces, no irregularities, as with Porsche 718.

Google Image Result for http://www.finecars.cc/typo3temp/GB/5a538db5f8.jpg

Last edited by Otto; 11-26-2013 at 09:36 PM..
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