2nd look at CYBERTRUCK

[freebeard]

"Modern standards"

edit: To be clear, it's a statement in support. Standards drift with time.

[aerohead]

Originally Posted by rmay635703

https://damogranlabs.com/2019/12/tes...-aerodynamics/

Does what this guy is saying make any sense?

In his conclusions, PS, he reveals the complete poverty of his intellect, aerodynamics-wise.
There's no indication that he can discern the significance associated with the difference between a sub-critical Reynolds number laminar boundary layer, and a critical Reynolds number turbulent boundary layer.
The difference between a smooth or dimpled golf ball. A fatal mistake.
I recommend that all members and guests consider the difference between 'toy' CFD software, and something like Dassault's Exa Powerflow CFD, which requires a 120-core processor to run on.
If the presenter hasn't spent $ 300,000 on their CFD, I would consider their results extremely dubious.

[aerohead]

Originally Posted by Vman455

Here is the Cybertruck* profile:



And here's Bild 112:



They aren't even close to the same contour. The curve between two points can take literally any shape--as we can see here with one curve and one line--and "matching" two points doesn't tell us anything about the aerodynamics of this truck.

*First prototype; video leaked last month purports to show a second closer to production-ready.

1) You'll need an image which better reflects CYBERTRUCK in true length fidelity.
2) Tesla Motors offers a long-distance, telephoto image of the chassis which is more dimensionally accurate. That's what I chose to work from.
3) Then one must represent CYBERTRUCK @ 8-inch ground clearance, which I've done, and is viewable at John Gilkison's You-Tube videos. No other extant photographs of CYBERTRUCK exist which represent the 8-inch GC configuration.
4) Only then can one do the proper x-ray overlay comparison, and I promise you that from CYBERTRUCK's roof apex, to the top of the tailgate, it's a perfect match to the FKFS contour I referenced. And I believe that I've already provided the necessary caveat about the traveling separation bubble which would occupy the void between CYBERTRUCK's upper aft-body surface and the FKFS geometry. Which may be a source of your dissonance.
5) As long as the flow is reattached by the time it leaves the vehicle, the profile has accomplished the aerodynamic pick and shovel work.
6) Fachsenfeld and Kamm found this during comparison tests between their segmented K-form, 'slope-top' half-body, and Walter Lay's 'straight-top' segmented half-body. You'll have all that in Fachsenfeld's book.
7) The same 'trick' is being approached with OEM tonneau covers on the RIVIAN R1T, Cadillac Escalade, RAM 1500 HFE, and Holden Commodore VT Ute.

[aerohead]

Originally Posted by freebeard

Not a match for Bild 112, but mainly because there is no plan taper.

The peaked roof doesn't [appear to] add frontal area, but it has severely compromised rear headroom. The peak angle is 204° so the brake is only 24°. The long vortex generating edges fore and aft reduce the air that goes directly over the top. There is no bed/cab gap.

1) CYBERTRUCK has six body widths.
2) From nose to tail, the body is broken into five different planes.
3) It absolutely has plan-camber and plan-taper.
4) The $ 1 HOT-WHEELS die-cast model even demonstrates this architecture.
5) Consider the roof peak in connection with DOT/ NHTSA roof-crush, rollover requirements, and structural (truss ) triangulation.
6) The air comes off the top of the windshield at an 74-degree angle of layback.
7) The air comes onto the roof at a declination angle of 6-degrees, a 22-degree turn.
8) The air leaves the top-rear at 9-degrees ( Ahmed's drag-minimum ).
9) The beltline is positively inclined @ 2.75-degrees,on a tumblehome'd ramp, perhaps developed in R&D to 'tune' out edge-vorticity, one of the most critical considerations which can be considered for a fastback. An industry first ( hope to know one day ).
10) You may want to postpone any comment as to edge vorticity, anywhere on the body, until after careful consideration of the pressure gradients they're immersed within.
11) Yes, the cab-bed gap on Spirit cost 16-counts.)
12) I've not sat in the rear of CYBERTRUCK and have nothing to contribute on that topic.

[aerohead]

Originally Posted by freebeard

It's all mooted by the pre-production prototype.

Overall dimensions may differ, flat panels are now convex, and the A-pillars are compromised by mirrors and a wiper.

1) I'll say zero change with the wiper.
2) Their mirrors are as good as they get. 10-counts would be reasonable.

[Piotrsko]

I believe they did a batch of either computer simulation, or possibly a couple of mock up runs in a tunnel. They are engineering geeks with a vast budget and a huge anal jerk for a boss so this thing is as clean as you can quickly get to for the proposed task using a minecraft template.

I think aerohead is just looking to see what they did data wise since Elon doesn't share his toys or data well. Say what you will, but aerohead GROKS this stuff at least as good as Irv Culver, and gives me the same headaches when I listen

[Hersbird]

Originally Posted by freebeard

Not a match for Bild 112, but mainly because there is no plan taper.

The peaked roof doesn't [appear to] add frontal area, but it has severely compromised rear headroom. The peak angle is 204° so the brake is only 24°. The long vortex generating edges fore and aft reduce the air that goes directly over the top. There is no bed/cab gap.

It does have good headroom in the rear because they gave it silly high headroom in the front so they could make the cyberpunk look. The whole top 8" is just wasted frontal aera.

[aerohead]

Originally Posted by Hersbird

It does have good headroom in the rear because they gave it silly high headroom in the front so they could make the cyberpunk look. The whole top 8" is just wasted frontal aera.

Cybertruck's actual overall body height ( without ground clearance ) is 59.85-inches.
Rivian's is 64.6-inches.
GMC HUMMER EV is 66.1-inches

[freebeard]

The whole top 8" is just wasted frontal aera.

Pre-Virgil Exner, Chrysler demanded enough room to wear a fashionable hat while driving. maybe fashionable hat will have a comeback.

[aerohead]

I'm goin' for the hat AND the car!
https://www.pinterest.com/pin/324118504403259086/