Tesla Cybertruck: Video on aerodynamics is wrong, says fluid mechanics prof
For electric cars, design is critical.
The Tesla Cybertruck’s unique design could hold more benefits than first appears. An independent analysis posted via a video this week suggests that beyond looking like something out of Blade Runner, the truck could offer surprisingly good aerodynamics.
The video, from YouTube account “Aerospace Engineering,” shows the Cybertruck could have an air-slicing drag coefficient reaching 0.38. That means it could move through air smoother than a ‘90s-era Ford F-150 pickup truck. For range-conscious consumers who don’t want to charge up as often, that could be great news.
But fans may want to temper their expectations.
An expert in the field — Chris Baker, a professor of environmental fluid mechanics at the University of Birmingham — tells Inverse that the video (see it above) probably doesn’t reflect its real-world performance, in part because of how the 3D model is positioned in the simulation. Baker went as far as to say he “didn’t find” the video’s simulation “at all convincing.”
It cuts to the heart of a question with increasing interest: how efficiently does a given electric car move through the air? A more aerodynamic design can mean a more efficient use of resources, which could mean fewer trips to the charger. With range anxiety a big concern for electric vehicle buyers, squeezing out every drop of metaphorical juice from the battery is vital.
Little wonder then that fans are building their own 3D models, trying to work out ahead of time how Tesla’s latest vehicles stack up.
Tesla Cybertruck: a performance powerhouse?
Tesla’s upcoming all-electric pickup truck, due to start production in late 2021, turned heads when it was revealed earlier this month at a flashy event at the Tesla Design Studio in Los Angeles. CEO Elon Musk, flanked by flamethrowers and lasers, took the wraps off a vehicle he’d previously compared to something out of the movie Blade Runner. Prices are set to start at $39,900, and range is set to go as high as 500 miles per charge.
Despite acting as the final part of a three-part plan to bring electric vehicles to the masses — which started with the Model 3 sedan and will continue next summer with the Model Y compact SUV — the Cybertruck doesn’t really bear resemblance to almost anything on the road. Musk noted via Twitter in the aftermath that this is almost out of necessity. The truck is built with 30X steel that’s been cold-rolled, making it incredibly tough but also difficult to stamp with a tool.
The truck’s angular shape could hold even more benefits, a video uploaded Thursday suggested. YouTube account “Aerospace Engineering” modeled the truck using computational fluid dynamics software, and found some interesting results, as seen above.
At 40 mph, the air going over the car appears to flow smoothly. In this case, although straight lines are “normally a bad idea,” the angle is “shallow enough” to avoid issues.
Although the simulation is expected to offer harsher figures versus real-world testing, it suggests the truck should cut through air better than its competitors. The video shows a drag coefficient reaching 0.38 as speed increases, a figure used to measure how easily a car glides through the air where lower is better. The YouTuber suggests that, because the simulation is imprecise, it could reach as low as 0.3 in real-world tests.
What does that mean? For comparison’s sake, the 1997 Ford F-150 had a drag coefficient of 0.45. The 2018 RAM 1500 has a rate of 0.36, which the firm declares as best-in-class. That means, for a pickup truck, the Cybertruck could cut through the air surprisingly well.
“The results I’m getting, I’m sure it’s better than this in real life,” the YouTuber notes. “I have run other cars and they don’t get near their claimed figures.”
As of Friday, the video was on the front page of the Tesla Motors subreddit, where it had received over 200 upvotes.
“This is why Tesla fans are the best,” said a Reddit user called “jabblack.” “No one would do this for any other vehicle.”
Tesla Cybertruck: hold your horses
Unfortunately, the figures might not look so favorable in reality. Chris Baker, the professor of environmental fluid mechanics, tells Inverse he “didn’t find the CFD at all convincing.”
" It just doesn’t look like a fully resolved solution
“It is obviously a pretty clunky code, and the way that the model is mounted in the air above the ground will make the underbody flow patterns all wrong, which will affect the rest of the flow,” Baker says. “From my perspective, it just doesn’t look like a fully resolved solution. Also there was an absence of three-dimensional effects — I would expect longitudinal trailing vortices behind a rear slope such as this. So I wouldn’t trust this at all in a quantitive way.”
Inverse reached out to the original YouTuber for a response ahead of publication.
Drag coefficient has been touted as a big area of focus for Tesla’s vehicles. Where the 2012 Model S came with a coefficient of 0.24, Musk aimed for a drag coefficient of 0.21 for the Model 3. The final vehicle reached 0.23.
The company’s marketing for the Model 3 has focused on actual range measured in miles, versus the Model S and X which are sold based on the size of the battery pack. That’s because, as of October 2018, the Model 3 was estimated to travel 60 more miles on a 62-kilowatt-hour battery versus a Model S with a similar-sized battery.
Beyond the Model 3, Tesla has been keen to advertise its vehicles’ drag coefficients. It touted the Semi truck as having a coefficient of 0.36, which it highlighted is lower than the Bugatti Chiron’s coefficient of 0.38.
It’s perhaps little surprise that, for the company’s next highly-anticipated vehicle, drag coefficient is back in the spotlight. Analysis from CFD specialist Wouter Remmerie received over 100 comments on LinkedIn this week, after he concluded that the Cybertruck would offer a coefficient of 0.48. Another analysis shared on the Infographics subreddit this week arrived at a figure of 0.47.
But while these fan projects make for interesting discussion about an oddly-shaped vehicle, it could be missing out what matters most. Baker says that focusing on the drag coefficient could ignore some of the other factors that influence an electric car’s efficiency.
“The drag coefficient as a concept is useful, but it is only one point of reference,” Baker says. “It says nothing about how drag varies with small cross winds, how the vehicle handles in cross winds, what the overall energy consumption is.”
Tesla has not given a figure for the Cybertruck’s expected drag coefficient, but with its previous focus on getting that figure down low, it’s perhaps not too surprising that fans are seeking to work out the figure for themselves.
Update 12/2 5 a.m. Eastern time: An earlier version of this story described the Cybertruck steel as being cold-rolled 30 times. It has now been corrected.