View Single Post
Old 04-24-2020, 11:34 AM   #44 (permalink)
aerohead
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,861
Thanks: 23,922
Thanked 7,207 Times in 4,640 Posts
'current cars'

Quote:
Originally Posted by JulianEdgar View Post
I am sorry, but are you seriously suggesting that wind tunnel testing of wheel drag, performed on a 1982 car without its wheels turning, is somehow relevant to modern cars?

Wind tunnels now test cars with a moving floor and spinning wheels. They do this for good reasons. I think this is probably the major reason that the research results have changed so much over the last decade or so.

The airflow patterns under a rough underside car like a 1982 Trans Am Firebird would be completely different to any modern car. The latest tech papers show that car drag can be influenced by how the wheels and under-car airflow interact.

I also note that "Index of Phil Knox Aerodynamic Seminars & Mod-data lists,under, Mod-data Lists: #7", as far as I can see, largely references material from the 1960s. As I said, old info is always interesting, but to apply it to current cars, when in fact current tech papers disagree, is in my opinion, not wise.
*Perhaps we might establish a cut-off date for 'current' cars,before which,we'd discount published drag coefficients.
* Additionally,so as not to disrespect the best efforts of the top investigators of the day,we might re-test a sampling of specific vehicles,in rolling-road wind tunnels,and publish back-to-back results,highlighting the actual difference in drag measurements,on a case-specific basis.
*Since 'current' vehicles might include drag coefficients upwards of Cd 0.70,it would be very interesting to see drag variability associated with rotating,versus stationary wheels.
*Contemporary aerodynamicists painting with broad-brush commentaries with respect to the inferiority of non-rotating wheel drag measurements have an obligation to provide specificity.Context. It's a slap in the face otherwise.
*I reviewed an online article about the significance of the aero wheels on,I believe,the Tesla Model 3.The conclusion of the investigation would be a 'fail',historically,by SAE metrics,unless considered within a very narrow interpretation of language used by the reporter.
*Wheel drag contributions have been part of the automotive literature since 1922.Advancements and refinements in testing are a natural progression,and welcome,however, contemporary investigators may not want to inadvertently disrespect the very shoulders they stand on.It's matter of simple courtesy.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
The Following User Says Thank You to aerohead For This Useful Post:
California98Civic (04-24-2020)