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Old 02-26-2024, 10:48 AM   #818 (permalink)
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' new Cd from tail '

Originally Posted by Phase View Post
What’s my new CD?
1) The tail relies on turbulence-free onset flow in order to perform to it's maximum effect.
2) We'd really need the full belly pan, diffuser, and full rear skirts to experience that kind of quality flow.
3) Most published boat-tail research findings are predicated upon the test vehicle having laminar flow ahead of the tail extension, top, sides, and bottom.
4) The Windsor Body boat-tailing research recently reported by PhD Jeff Howell et al., accommodates the tail with this laminar flow.
5) As to the lack of an 'underbody' on your tail, Lawrence Livermore National Laboratory's boat-tail research reported that a 32-inch, 4-sided cavity, had virtually the same drag reduction as a 48-inch, 3-sided tail ( wasting 16-inches of elongation potential ).
6) As we discussed a couple years ago, if you'll do the belly, diffuser, and wheel skirts, the IONIQ will be around Cd 0.20.
7) just the 10-inche difference in length between today's M-B EQS Sedan, and EQE Sedan is Cd 0.20 vs Cd 0.22.
8) Although never published, the difference in 'length' for the active tail on the 2016 M-B IAA might be in the range of delta- Cd 0.020 as well.
9) Just the approximate, 8-inch diffuser extension on the 2022 M-B Vision EQXX = delta-Cd 0.010.
What you're doing is 'qualitatively' the right thing for lower drag, but it needs careful handling 'upstream', and a 'floor' for the cavity extension.
After that, the drag will vary as a function of wake area, compared to the OEM wake area.
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