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Old 10-27-2012, 03:10 PM   #373 (permalink)
aerohead
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New Images

I have done a few additional pictorial representations which I wanted to add just to muddy the waters further.
The first two are for 2-dimensional flow sections and struts which illustrate the significance of the aft body to low drag and then,the significance of the thickness ratio to drag.In streamlining,there is always a 'sweet-spot',where both pressure drag and skin-friction are both at their minimums.
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The 3rd image is a pictorial representation of Lehmann and Kosin's fuselage
drag table posted earlier in the 'Template' threads.
You can easier see how the aft-body of the fuselage reduces the Cd by 5.66X.Of course,in an automobile the overall drag will include the cooling system,wheels,interference drag,etc.,however you can clearly see why the aft-body is so significant to low drag.
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The 4th image is "Sparrowdynamics",or a look at 'Bounding' flight which is technique used by small birds flying into a headwind,whereas the wingbeat is suspended momentarily,with wings completely folded,and the bird's body taking on the form of a streamline body of revolution if you will,which if a smooth,rigid surface would have a drag coefficient of Cd 0.04 sans tail feathers,legs,beak,head,and wings.
You can see how Pierre Julienne or Santos-Dumont might have been inspired by bird flight ,as was the Lillianthal Brothers,when designing their airships.

The image is adapted from an illustration by Ad Cameron for Reader's Digest Edition,'BIRDS' Their Life-Their Ways-Their World,copyright 1979,p.30-31.
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Last edited by aerohead; 10-27-2012 at 04:55 PM.. Reason: add PS
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