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Old 05-16-2022, 01:56 PM   #294 (permalink)
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Cd 0.19

Originally Posted by Phase View Post
I mean Iím removing side mirrors so that would put that at 19 right there give or take

I looked at the bottom of my Ioniq again though, sure itís not perfectly smooth, but itís extremely straight and none of the part under the car buldge out to disrupt airflow. I think Hyundai did the best they could with aligning the muffler and everything underneath to be extremely flush without covering it with a panel. Even the muffler thatís laying horizontally is angle slightly like a rear diffuser to guide the air. Obviously it can be improved.

If smooth under body and rear skirts/spats can put it at 20, then no mirrors 19, I wonder what the hypothetical cd could be with an extended spoiler and mini box cavity in the rear. Then duct tape the door handles smooth and use racing tape to cover every body panel crack 😂
1) Decades-old mirrors would ( have been reported at ) delta-Cd 0.015. Giving you Cd 0.225.
2) TESLA-quality mirrors would be delta-Cd 0.010, giving you Cd 0.23.
' With a long diffuser, a notable reduction in drag can be achieved with a very small angle... However, this effect is only assured with a very smooth underside.' Dr.-Ing. Wolf Heinrich Hucho, 2nd-Edition, page-144
3) No belly-pan, no diffuser, and lose 30-counts.
Belly pan with diffuser, rear skirts, and mirror delete: Cd 0.19-to- Cd 0.195.
The 2012 Coventry University testing of the Audi A2 box-cavity showed a 2% delta Cd, from a car with Cd 0.288.
2% from a Cd 0.24 car would be 0.0048, yielding Cd 0.1852-to- Cd 0.1902
I taped all the seams on SPIRIT and it showed zero difference in the wind tunnel. General Motors allowed 0.007 for these 'features'.
' Qualitatively, the effect of the length upon the aerodynamic drag is similar to that for the ( streamline ) body of rotation.' W.H. Hucho, 2nd-Ed., pg 142
' the drag reduction from an elongated tail varies almost linearly with the reduction in cross section area.' Jeff Howell et al.,' Streamlined Tails- The Effects of Truncation on Aerodynamic Drag,' Loughborough University, 2020, Abstract, SAE Paper 2020-01-0673
' base pressure also depends upon the angle at which the flow separates from the contour.' W.H. Hucho, 2nd-Ed, page- 141
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