Independent Cybertruck Drag Coefficient Analysis Yields 0.34 Cd

[Administrator]

Posted by pkrcm on Reddit.

Cybertruck drag analysis with Ansys Fluent. Coefficient of Drag = 0.34 (2.8m poly-hexcore cells, k-omega SST turb. model)

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[Ehninger1212]

When did Elon claim .35? thats pretty freaking good.

 

[TheLastStarfighter]

When did Elon claim .35? thats pretty freaking good.

He didn't... he said .3

I expect a big part of the size reduction on the final vehicle will be more standard wheels that fit inside the arches. You can trim a couple inches there, and get rid of a lot of the noise in the diagram above.

 

[cyberhunter]

the fact that EVs can have virtual smooth undercarriage contributes a decent amount to their lower drag coefficient. For the CT the sloped rear helps a bunch. A sideways teardrop is an excellent aero shape for a vehicle and the CT is very similar (although angular) to a sideways teardrop.

 

[Diehard]

I wanted to see this bad. Thanks for sharing. I always thought of rigging something for long highway travel like a triangle up front and in the back. Now I am not sure how much of a difference it makes in front but it looks like it would definitely help reduce turbulence and drag in the back.

 

[Cyberman]

Nice. Wish I had something smart to say about it, but I don't really know what it means. But it's pretty cool. I think. It's another feather in the CT cap. Yeah, less wind drag than its dino cousin, the F150.

 

[Jhodgesatmb]

Nice. Wish I had something smart to say about it, but I don't really know what it means. But it's pretty cool. I think. It's another feather in the CT cap. Yeah, less wind drag than its dino cousin, the F150.

A couple of things. When Elon Musk was interviewed recently he spoke about the coefficient of drag and mentioned a couple of these factors. I do not recall him giving a value. When he unveiled the CT he said the value might go as low as 0.30 which would be really, really low for a truck. Seeing this calculation and having it be very close to what Elon Musk said about it tells me 2 things: (1) it increases the likelihood that Elon Musk knows what he is talking about, and (2) it increases the likelihood that this value is in the right ballpark. As for what the value means, it means that the predictions that Elon Musk made for CT range are probably achievable since drag has a lot to do with efficiency and subsequently range.

 

[Diehard]

Do you guys think CT is lighter at higher speed due to having less air pressure on top like aircraft wings? Or you think the impact is negligible because there is a lot less surface area and speed?

Edit: By ”lighter” I am referring to reduction of vertical stress on tires due to lift.

 

[Jhodgesatmb]

Do you guys think CT is lighter at higher speed due to having less air pressure on top like aircraft wings? Or you think the impact is negligible because there is a lot less surface area and speed?

An aircraft's weight doesn't change just because there is a lifting force on it, and the lifting force is the result of different pressures on the bottom and top of the airfoil. I have never done an analysis of a vehicle shape. Maybe the OP has.

 

[Diehard]

An aircraft's weight doesn't change just because there is a lifting force on it, and the lifting force is the result of different pressures on the bottom and top of the airfoil. I have never done an analysis of a vehicle shape. Maybe the OP has.

I probably should have worded it better. The question is, would it reduce energy consumption due to reduced stress (and may be contact area) on the tires?

 

[Crissa]

What you're asking for is 'is there gravity reduction on the tires because of aerodynamic lift?'

^-^

-Crissa

 

[firsttruck]

What you're asking for is 'is there gravity reduction on the tires because of aerodynamic lift?'
-Crissa

Won't any aerodynamic lift also be accompanied by more aerodynamic drag?

 

[Crissa]

Won't any aerodynamic lift also be accompanied by more aerodynamic drag?

Any lift would come from drag, yes. Hard to know if it's necessary drag or not, though, so hard to know if it's 'more'.

Surface effect flight is a thing, and you can end up with less total resistance that way. https://en.wikipedia.org/wiki/Lun-class_ekranoplan

-Crissa

 

[Akgolf]

Wow compared to .59 for the F150 that’s great!

 

[Diehard]

What you're asking for is 'is there gravity reduction on the tires because of aerodynamic lift?'

^-^

-Crissa

More like Friction reduction. If the lift works against the weight, theortetically there would be less contact. It would be like having more air in the tire or smaller economical tire. Bothe of those usually result in better gas millage.