Drag Coefficients ( which to use )
 

I figure this is going to come up at some point so I wanted to mention it.
Fluid Dynamics,of which aerodynamics is only a branch of study,is an interdisciplinary body of study.
"Drag coefficients" while always used,can be different animals altogether.
In aviation,structures might be referred to in terms of the area of flat plate parallel to flow.
Also in aviation,an airship like Zeppelin's latest,or Goodyear's,Fuji's might be rated with a frontal area Drag coefficient,but it might also be rated with a volumetric drag coefficient.
Frontal drag coefficients must be specified as to whether they are at,below,or above critical Reynolds number.
In marine science,a body might be described by a frontal drag coefficient,a volumetric drag coefficient,or a skin-friction drag coefficient.
An example,which appears in the FLOW-IMAGES is the Gentoo Penguin with:
Frontal-area drag Cdf 0.07
Volume drag Cdv 0.031
Surface drag Cds 0.0044
Here's another look at the penguin:
http://ecomodder.com/forum/showthrea...t-11504-2.html

Gallery-8 2nd row,2nd from right
 

the address wasn't specific enough to isolate the penguin,you'll find it at the address above in the title box.