Thread: CdA list
View Single Post
Old 07-29-2020, 04:23 PM   #163 (permalink)
aerohead
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 12,923
Thanks: 20,702
Thanked 6,323 Times in 3,922 Posts
frontal areas

Quote:
Originally Posted by tasdrouille View Post
One thing I noted though. In every single case where the frontal area was stated, the 0.81 correction factor on h * w you used gived an overly optimistic figure.

I recall reading a post by phil, must have been of of his aero seminars I'll have to search a bit, where he said to use 0.87 or 0.85, can't remember exactly.

Edit: it was from Aerodynamics Seminar # 6 - by Phil Knox
CAR and DRIVER used to be the 'source' for both Cd, and Af. Ever since Csaba Csere retired as technical editor there's existed a black hole for this information. It's almost a miracle nowadays to see aerodynamic specifics mentioned at all in reporting.
When Don Sherman returned to CAR and DRIVER, and did the 'Drag Queens' article from the A2 Wind tunnel, they used telecamera files and a SIEMENS software package to count pixels, and come up with frontal areas, the first time in decades to report frontal areas.
As cars have given up some ground clearance and grown obese in tire widths, the net fraction of frontal area has grown from around 0.81 of Hucho's mid-1980s, to around 85.5% of gross area for contemporary automobiles, as in the case of the Tesla Model S.
It's an estimation only, and as mentioned by members, 'way out ahead of nothing.'
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote