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Old 12-02-2019, 01:05 PM   #79 (permalink)
aerohead
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Cd change

Quote:
Originally Posted by redpoint5 View Post
That guy claims the truck has something like a .41 Cd at 60 MPH, and somehow it drops to .3 at 88 MPH. How does Cd change with speed? I thought it was a constant value.
Up to the debut of the Cybertruck,there's been nothing in the aerodynamic literature to suggest that between 20-mph,and 250-mph,the drag coefficient would ever change.Once beyond the supercritical Reynolds number the Cd would remain constant,until transonic flow,and attendent compressibility effects began to drive the drag higher with localized shockwaves.
Also,in Justin W. Martin's CFD presentation, he's saying that the Cybertruck's Cd is below nearly any 1/2-ton pickup,with the 2019 RAM 1500 @ Cd 0.357 as the current industry benchmark for lowest drag.
We really need to see the Tesla at 8-inches ground clearance,with its body inclination optimized for highway cruising,as Ford did with their Probe-IV and Probe-V concepts.It's entirely possible that the Tesla's belly can become a full-length diffuser, front airdam can deploying downwards,and same for an optimising rear diffuser.Tires partially shielded.
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