Audi's tunnel is also aeroacoustic, so you can do measurements of noise generated by wind around the car. I've tested cars in there myself, and it's pretty much silent, even with the wind doing 140kph - until you put some big bluff thing in there to disturb the wind!
@@robertpalin5878 It's the way that a microphone capsule itself responds to the wind that is the problem. I'd guess that the reason it's quiet in there is that the tunnel itself is carefully made to be aerodynamic, to be efficient.
Looking at Jack standing next to another human (other than Robert) and especially next to an old sedan, you realise just how massive he is. A tower of a man. Really puts his back seat legroom comparisons into perspective. Thanks guys. 😊
Drag Force = Fᴅ = ½𝜌𝜐² 𝙲ᴅ𝙰 (in Newtons ISO, kg⋅m/s²) 𝜌 = Density of the air (1.204 kg/m³ at 20℃) 𝜐² = Speed squared (in ms⁻¹) 𝙲ᴅ = Drag coefficient (Audi GT = 0.24) 𝙰 = Frontal Area (in m²)
Imogen just occasionally using terminology that gives away her background as an actual aerodynamics engineer 🙂 making her the perfect choice to present this!
That’s because there are many many people who choose to pay for it through Patreon, so Robert Llewellyn has been able to grow from a one-man band 11 years ago to a whole team of professional people working on the channel, and it will hopefully reach 1m subscribers this year or early next. I’ve been watching since the beginning, but only signed up as a patron this year. I even sit through the shorter ads to make sure the channel gains a bit more revenue (the 3 min spammy ones I usually skip, although sometimes just let them play through while I read the comments) The debut video and early videos are always worth a re-watch, because Robert is a fantastic presenter and knows his stuff.
Great to see that you continue to emphasize the importance of aerodynamics - and great to see that it is finally coming back. I hate that something as shallow as fashion could be seen as more important than the laws of physics. Also - that classic Audi 100 was always a big favorite of mine - I was 10 years old when it was released - and the aerodynamics of it was always the key reason for me liking it. More stuff like this please!
The 10 year old me fell in love with slippery aero design when the 1983 Audi 100 was introduced, not only by the cool futurist looks, but also the plain rationality of it - make the car aerodynamic and save fuel - what´s not to like? Therefore, I have been quite upset over the last 25 years as big boxy energy gulping SUV:s suddenly was the norm and aero efficiency was forgotten about. Good to finally see good old aerodynamics getting a well earned comeback! Great episode!
@@NeilBlanchard actually thats inverted, the aerodynamic drag is by far the biggest drain on the battery. The drivetrain efficiency is over 90% in most electric cars already.
@@FreekHoekstra I am talking about the overall efficiency - if you compare EVs with ICEs, the largest improvement comes from the drivetrain, and once that is "solved", then the next biggest gain comes from aero drag. And as was commented on, if the EV drivetrain is NOT at peak efficiency, then even the best aero drag can't salvage the efficiency.
@@eskanderx1027 Aptera is not something an Audi SUV customer will cross-shop, though. They care a bit more about staying out of hospital than being THAT greenwashey.
@@Cloxxki Composite monocoques are incredibly strong and since Aptera are yet to do physical crash-tests (simulations only to this point) your "staying out of hospital" comment is pure supposition. Let's wait until we have some facts on which we can base opinions, before making uninformed judgements.
I worked as an undergrad in a wind tunnel at the NPL at Teddington. Enjoyed it so much. The smoke only comes out when the client’s on site. It’s pretty much just because it looks cool. It serves no qualitative purpose.
@@deus_ex_machina_ primarily you measure the force exerted on the test object I think. Flow visualisation is useful when you want to know WHY something has an effect though.
Interesting stuff. I'm guessing since vehicle speed plays such a large part you don't really have to focus on aerodynamics so much for a delivery truck with it's neighborhood speeds and stop and go driving. Those vehicles probably benefit more from regenerative breaking, lighter construction materials, maybe solar on their relatively large roofs.
Well yeah GM EV1 was build back in 1996-1999 and also had low drag coefficient of cd=0,186.. VW XL1 (2013-2016) had a cd =0,191.. The thing is Tesla also proved with the Tesla Semi that are a lot of areas that can be aerodynamically improved to get a more efficient range on the 18 wheeler, like cover for all wheels, slicker shape of the head-cabin, different wings under the trailer to channel & flow of the air etc..
@@GregHassler This content is owned by the Author "TheOtherJesse". If you read: "Content in the public domain may not have a strict legal requirement of attribution (depending on the jurisdiction of content reuse), but attribution is recommended to give correct provenance." This means it depends on the Author to ask for provenance or not. No, public domain is not automatically as you said. But here the Author said clearly: "I grant anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law." So, it should be fine. Always look for the source guys.
It should be noted that CFD requires multiple dimensions of approximation to work at all. So the volume around the car is divided into millions of tiny cubes in the model, and likewise the airflow, and most critically the differential equations governing the conservation of momentum are made up of an infinite series of terms, so a perfect solution for any step is impossible to achieve, even if you could somehow start with 100% accurate initial conditions. So the models work only with a “close enough” approach, and have dramatically improved as computers can handle smaller cubes, finer time steps, and more terms in the equations, but can never resolve everything. Which is why engineers always end by building physical models and testing them in “real” conditions. All the same applies to weather and climate forecasting, btw - computers are incredible, but they cannot work miracles.
CFD has a lot of limitations; witness the huge expense on simulations in Formula 1 design that still result in huge variation in car design and performance each time the rules are changed a bit. They rely hugely on testing and opex to refine things
Surely, it critically comes down to a battle between maximising aerodynamics and DESIGN! You don't want your Audi to look-and be, completely preposterous - and, crucially, you want it to look like an AUDI!!!
@Simon de Haas - absolutely, but my point was that those limitations can only be mitigated a little with more advanced computing, because of the nature of the non-linear equations within the model. And I didn’t even go into the issues with establishing the initial conditions in terms of pressure, air density, humidity, temperature and direction. Many people have a naive belief that we can just keep throwing computing resource at a problem and we can get “more accurate” results, but whilst we can improve the models we will never remove the need for physical models and real world testing. Formula 1 presents orders of magnitude more difficulty to aero designers than ordinary road vehicles of course, with speeds, accelerations, decelerations and interactions with other cars all presenting huge challenges. And I won’t say anything about the fact that some teams stretch the definition of what is allowed within the regulations 😀
I've been a convert to the benefits of reduced drag when I built my MkIII Midas Gold. Initially I drove the completed car without the under-trays fitted. When passing juggernauts there was a definite twitch felt twitch felt at the steering wheel. Access to a friend's pit allowed me to fit the under-trays. The difference was immediately noticeable, no twitch when overtaking juggernauts and the car felt much smoother. You had to watch out as it was too easy to exceed the speed limit without realising it. Thank you, Gordon Murray for you input to the design! All this was in 1986.
The Aptera getting 10 miles per kilowatt hour is a perfect example of how critical aerodynamics can be. (Most EVs get 5 or less, with upper 3's being the average)
It's a perfect example of how critical all things related to efficiency is. The Aptera is more aerodynamic, lightweight and has in wheel motors. It was designed from scratch with the idea of efficiency, not focusing on how cool it looked or making sure it had 4 or 5 seats.
..and a clear reminder that, relatively speaking and despite progress, aerodynamic efficiency at Audi (and almost everywhere) is still an afterthought.
I am really interested in the second car Aptera does which will have 4-5 seats and 4 wheels, and probably still be more efficient than the others. Rumor says they may be able to add a third seat in the smallest battery configuration of the initial car which help break it out of the niche of two seaters.
@@flannel2699 More like one important factor, next to everything else (looks, comfort, performance). Aptera can get away with their so high focus on aero efficiency because they are essentially aiming for that pretty niche market of people who are fully focused on range and low fuel costs. If Audi or other established car manufacturers would switch to aptera like designs, they'd see their sale rate plummet quite quickly. They really need to thread the needle and find the right balance between all those factors.
@ 4:40, A single cheek slide certainly minimises any friction. Even less if you clench. Look at the distance that Imogen pulled on Jack. She can really hold a slide! This was an extremely interesting topic. Very informative. I'd like a Sono Sion, but can't go past the aerodynamic efficiency of the Aptera!
Excellent presentation Jack & Imogen. I didn’t realise Jack was such a heavy smoker. I sincerely hope that aerodynamics (and other disciplines) continue to improve the efficiency of our vehicles, and that cheap fuel never again compromises car design.
Worth pointing out (given all the comments below about efficiency of the Audis) that the Teslas are particularly good in their AWD versions because of their "hybrid" motor setup. They use permanent-magnet motors on the rear wheels to do most of the work, where the running efficiency of the permanent-magnet motor outweighs its relatively high running drag (when coasting, you can't prevent inducing some waste current in the coils since the magnet is always "on"). In front, they use induction motors, which are not as efficient, but have quite low running drag, since you can turn off the current that induces a magnetic field in the rotor. Then you use the permanent magnet motor in the rear to do most of the drive and regen braking (catering to its strengths) and turn on the induction motor in the front when you need AWD traction or brief acceleration (again suiting the motor to the task). Very clever, and resulting in a car like the Model Y which is AWD, but still gets hwy eMPG of 117...compared to the e-tron quattro which gets (gulp) 77 eMPG on the highway (and in the real world, highway eMPG is what most affects range for the vast majority of drivers). Design matters!
The Fully Charged videos are always well put together and presented. This one no exception and gives excellent coverage of a topic too often ignored. Thank you Imogen and Jack for making it easy to understand.
I t's about time that aerodynamics has risen to the forefront. It is also interesting, that it's AUDI that you chose to show the development of cd. Thanks
Very enjoyable and informative team ( just wanted to see them stand back to back 😁) . Interesting to see just how crucial the aerodynamics are in vehicle design now, just imagine how much gasoline could have been saved over the years if it was always applied🤔
Those big 4x4 travelling at speed on the outside lane make excellent aerodynamic wedges to follow. I regularly achieve 5.1MKwH behind them. Coaches are also good. A lot depends on how you drive. As a pilot I know all about drag and how to exploit the effects of air resistance. The difference between 65mph and 70 is noticeable. It’s about finding the sweet spot.
I suggest you produce a short with Jack (and potentially Imogen, if she was in the same position) addressing his perspective as he was operating the smoke gun and visualizing aerodynamics concepts, how it impacted his perspective. What's missing is the consideration of the conflict between shaping the vehicle to optimize the aero and optimizing the footprint, the inner volume. The noise treatment for the wing is brilliant, whether through the mic covers or post-prod.
It still amazes me to see the wheels looking like big fans and most all vehicles don't cover the rear wheels all the way to the lower rim. Maybe they are saving some improvements for the next model? We know they can do better than 0.20.
Maybe because Cd is only a one in a dozen different factors that ultimately contribute to range? Frontal area is a huge factor and he eluded to the fact that the design team wont make adjustments for the sake of aero. So corporate branding concerns outweigh efficifiency for some marques.
I can't understand why aerodynamics was not a priority before EVs. Why did we not add aero hub caps, retracting door handles and camera rear view mirrors years ago. 🤔
Back in the late 80s, I worked at a Subaru dealer for a while. The XT was the closest thing they had to a sports car. I can't remember what the coefficient of drag was, but I remember they were quite proud of it at the time.
It's funny considering the Audi e-tron GT is objectively bad in efficiency (202Wh/km) compared to a lot of electric cars. Hyundai, Tesla, Renault, Peugeot, Cupra, MG... All achieved 160-170Wh/km on similar sized cars. It goes to show how much the industries values this kind of testing, it's really one of the keys to making great electric cars.
I've been driving for a number of years, and my four favourite owned cars from yesteryear were a Citroen GS, an Audi 100, and my absolute favourites, my two Saab 900s. One an Injection, one a Turbo 16. All the cars had aerodynamics high on their list of priorities. All through those times I had been waiting for battery technology to catch up to the electric motor. These days, it's a VW ID.3. Maybe the next one is a Tesla. I love not having that unnecessary front grille that causes drag.
Such a pity that cars look so utterly ridiculous without a grill! Kinda like Lord Voldemort........!!! If you stare at the 'nose' of a Tezzler for any length of time it gradually morphs into something really quite scary.......
@@andymccabe6712 But they look even worse when they have one but don't need one. And I've never heard any adverse comments of Porsches and VWs with rear engines and no grilles. You get used to these things.
Glad to see a focus on efficiency on this channel, Its the fastest way to get more range for less cost and is more interesting and useful than how fast a car gets from 0 to 60. I want to know how fast Ev's can get from 500km of range to a 1000km for under 30 grand, now that is a metric worth knowing about.
They probably get there by having gigantic batteries. Big, heavy EVs like that are not a good idea in my opinion. They’re much heavier than their ICE counterparts that have similar or greater range, which is worse for the road infrastructure and worse for pedestrians and other road users in the case of accidents. A small, light EV with a small battery that provides modest range along with a larger ICE car for longer journeys would be a better combination for most families.
The sweetspot is a EV w/ 25-40kwh battery that gets 150-200 mile range but only costs $15-20K USD. No autonomous driving, no amazing 0-60 times just simple & reliable & efficient. Basically a model 3 without the tesla brand & gadgets
the answer to why you need a wind tunnel is to ensure that the computer flow simulation is accurate. Most flow simulation software uses particle emission simulation and a series of complex predictive algorithms to try to determine how the forces will load on a surface, and thus help to determine what the coefficient of friction and, thus, drag should be for a vehicle. But, because the sample size is somewhat low due to processing constraints and the algorithms can't perfectly represent reality, it is still necessary to build a model and chuck it in a wind tunnel to validate their predictions from the 3D computer model. So, it isn't that we can't simulate it, because we can. It's just good to acknowledge that our simulations still aren't quite up to the high bar that is reality.
Quality geek TV - Great combo with two presenters who have a genuine passion for the subject. I feel like there's been another move forward of late, keep it going 👍
Very interesting watch! But the market pushes companies into building SUV. A brick on wheels (with a bit of smoothing sure). Right now, I'm guessing if you gave people the choice between an electric A4 or an electric Q4 the latter will probably sell better. It's a hard task making a car as aerodynamic as possible within the market demand (like the car sizes, preference to regular mirrors and handles, etc).
You know what? I really like the Audi E-Tron shown here, however, I am too infirm to get into it without pain, and getting out is more difficult. So, for those who keep bashing and decrying the SUV style electric cars, have a thought for those of us who need to be able to get into our car without having to suffer for it. Once in, maybe the many thousands of people like me get comfortable, but dread getting out of the car. For me, this is important to have a higher car to get into easily. Up to now, it's the SUV, in the future, there may be something better that does not offend people because of its size.
@@BobH809 But by using an SUV, sitting in high chairs etc. you're only exacerbating your frailty. Edit: This didn't come out right, what I meant to say is that just like the higher bumper height of SUVs and pickup trucks necessitates ever more massive vehicles, similarly insulating yourself from the least bit of discomfort only makes it harder to function normally. It's a race to the bottom, basically.
@@BobH809 Well, I realise how it came off that way, but no, I'm emphasising the importance of functional movements in daily life, basically turning normal activities into physiotherapy. Upright Health's channel and Not Just Bike's video on 'The Gym of Life' are examples of the philosophy I espouse.
@@BobH809 Oh for sure I would never disparage someone's choice due to infirmity. To me the general market demand does not include ppl with disabilities or other difficulties. I'm guessing most SUV buyers do not get their car because it would be genuinely giving them pain if they didn't.
Great episode, Jack and Imogen make a great team. More of this please. Comparing your gait on sprinting back up the slope, Imogen clearly has a much lower Cd (not to mention CofG) than Jack. 😊
Brilliant video, nicely presented and really interesting to see where the future is heading. Cracking car as well, look forward to collecting mine soon once production delays are sorted.
For air density, you need to know the temperature, the altitude, the humidity, and the atmospheric pressure. Cooler air is more dense than warmer air. Air is "thiinner" at higher altitudes than it is at lower altitudes. Higher humidity air actually has *lower* density - which is counterintuitive, but it is. Atmospheric pressure varies, but this is probably the least critical factor of these. Below 250MPH, lower drag shapes have a *blunt* front end - and a pointy back end. This is because most of the drag is generated *at the back* of the vehicle. A low drag shape lets the air close back in behind the vehicle has pushed through - with as little turbulence as possible.
What I want to know is to quantify what a reduction in drag does to the range, so what’s the difference in range between a car with a drag coefficient of 0.3 and 0.24
Excellent episode, very informative and great to see these facilities in action! Also, the team-up between Imogen and Jack works really well 🙂 Small gripe though: OK to use "handwritten" text in the graphics, but is it necessary to keep them wiggling all the time?
I think frontal area is heavily overlooked. My boxy, non aero, brick of a windcatcher: an old Citroën 2cv (0.51) has the SAME drag as a shape optimized, windtunnel tested, Tesla model X (0.24). This is completely due to the fact that the model X has over twice (!!) the frontal area of that inefficient shaped car of mine. Let's make cars small and sensible again! The model X mini would be twice as efficient (and no, the y doesn't count, it's still slightly massive)
I remember a Dinky toy model of a land speed record car called the speed of the wind. If you look at many of the current designs they still show the same principles.
Wow... I hadn't thought about Dinky Toys since I was a kid. I used to love them. I think I still have a few in a box in the basement. They were made of metal with real rubber tires, so that last just about forever. Thanks for the memory! ☺
It's great to see someone as informed as Imogen do the presenting...you can tell from the way she seamlessly talks about nice laminar flow and separation she knows her stuff. So ironic that the company willing to host was Audi, whose EVs are utterly at the bottom of the pack when it comes to efficiency (eMPG). Perhaps they were hoping to use this forum to distract from that fact?
I remember speaking to someone in the late 80's who had been involved in some sort of auto racing. This man had absolutely no concept of drag or the drag coefficient formula. He adamantly believed that the only thing limiting a car's top speed was the gear box and the amount of straight track available. I was appalled.
Thanks team, we need more videos like this. The etron is not an efficient vehicle and has poor range.Mass and electric efficiency carry as much "weight" as CD. 2 examples; Aptera /mass 800 kg CD 0.13 700-1600km range (solar) Ford F150 Lightning/mass 3tons CD 0.56 range up to 500km /towing 200-250km (estimates). PS; this episode reminds me of Beyond 2000 and Tomorrows World.
Imogen & Jack make an incredible team for presenting this sort of scientific knowledge & artistic awesomeness, great episode 😄🙏🏼 Aerodynamics is cooler than I previously imagined 💚
I got to say “well, we are in Germany, it would be rude not to” for almost 17 years on and off, living in Hannover, Bergen, Bielefeld and Gütersloh. If certain obstacles were removed I would do my best to go back.
Like your phone. The most important part is battery degradation. Nio does battery swapping stations so you constantly have a new full battery within minutes
Great video !! Hope SUV's owners see it ! What's the use of electrifying 2 to 3 tons-heavy bricks ? ( do you hear me BMW/ Hummer/ GM etc etc ...of course you don't ahaha !) ??? Also hope the trend will change and people understand that our cars will need to look as much as possible like the APTERA or the Mercedes EQXX ;). Thanks for your videos !!! Bonne journée !
Worth considering velomobiles here. So aerodynamic, and so much lighter than a car, that they are around 80 times more efficient than a Nissan Leaf !!! And that means 1/80 of the cost to charge up.
It's amazing how aerodynamic features like wheel covers, undertrays, flush door handles and camera mirrors aren't more common on ICE cars. They would benefit*more* in terms of energy costs and emissions reductions in absolute terms than EVs do.
Possibly true, but the auto industry has grown fat on historically very low fuel prices, and people have got used to driving hulking great bricks around without giving a feck about it. That has changed only recently, but any car maker investing in new ICEVs is going to waste a lot of money, when their sales are dropping exponentially.
Question regarding your drag coefficient data. What is the A (area) used in the formula to calculate the drag coefficient? After all, we ar interessed in the lowest force being created when comparing cars :)
"A" = frontal area measured in square metres. If the front were rectangular when viewed from directly ahead (disregard the visual-perspective aspect of it), it's the width x height. With an irregular shape (which is more commonly the case), you have to do the math but it amounts to the same.
Cd gets multiplied with A. Which is why I always find it funny, when people congratulate HUGE cars with record-breaking Cd-values, when a small, less aerodynamic car will run circles around the big one, just because the frontal area of the whole box is half of the big car. Squeezing the last 0.01 Cd out of a car is nice and all, but buying a car which is 20cm slimmer will fix that manyfold.
Aerodynamics are so crucial yet manufacturers insist on producing wardrobes on wheels, gunging great SUVs looking like they were chiseled out of granite. The Toyota Bz4x being a prime example.
The great advantage of EVs over ICE vehicles is the flexibility of design that is possible. In an ICE vehicle you can't get away from certain structural requirements of having to using an engine, a clutch assembly, a gear box and a fuel tank. In EVs you can have a motor in the front, in the back or both. You can have two motors, three motors or four motors as standard. You can have the motors inside the wheels. You can have the motors front mounted, centre mounted, rear mounted or any combination of the three. And the same is true of batteries. They can be placed anywhere that there is space and can be used to change the cars balance and even be part of the structure. What's this got to do with aerodynamics? Well, if you remove most of the limitations of how you design a car by making the positioning of the "fuel" and the location of the traction device[s] (motor[s]) infinitely more flexible you can avoid the blocky, bulky, inefficient shapes that were once necessary to house the bits that make a car functional. The greatest current example is the Aptera Gamma. With batteries between 23kwh and 100kwh in size the streamlined build allows for 10 miles per kwh economy. Therefore even the 23kwh car can run for 230 miles. When my 2015 24kwh Leaf was manufactured it was advertised at 80-90 miles of range which maxes out at 4 miles per kwh. In actuality it was quite capable of 110 miles of range (4.9 miles per kwh) in normal use. Just seven years later and the Aptera can go more than twice that distance on a smaller battery. It's largest battery allows 1000 miles of range. With the addition of solar charging you may find that you don't have to charge the car for months at a time as it will acquire more energy sitting in the sunshine for a day than most people will use in a normal day. Therefore, it has surplus power that means the battery can be fuller every day than it was the previous day without having to plug it in at all. But, back to the plot. The aerodynamics of EVs have more potential than ICE vehicles because of the mobility of the components within the structure. If you want a Bugatti Veyron you just have to concede that it's going to have an enormous engine, a huge fuel tank, a clonking great gear box and chunky clutch assembly. That is going to be fitted into a frame that is built as a compromise between containing those elements and streamlining the shape. The original Bugatti Veyron had 1001 horsepower. It would use the first 250hp to get to 150mph. It took that much power to push it through the air. But, it then needed the next 751hp to reach 252mph. For stats nerds that means it averaged 1.67hp for every mph up to 150mph, then averaged 7.36hp per mph for the next 102mph. This is because it's aerodynamics were dictated by it's need to house necessarily bulky components. EV design minimises this issue. And as batteries achieve higher energy density the volume needed for any given capacity decreases. Look at the Renault Zoe. It went from 22wkh to 41kwh to 52kwh in six years while retaining the same battery volume. Just more evidence that EVs are the future and technical evolution in transport no longer requires the presence of fossil fuels.
Great work guys - Really interesting piece. I wonder how the same challenge looks for the world of vans, that are a way behind in the aerodynamics department... I think the Brick was most appropriate!
Details matter. For example, Fiat Ducato (sold as Ram Promaster in North America) Cd = 0.31, which is rather surprising for a vehicle of such a shape. Obviously someone paid attention when designing that one. The problem, of course, is the frontal area. A great big box that someone can stand up inside, there's only so much that can be done.
kudos to whoever's in charge of sound! it's gotta be a pain in the butt to record sound in an active windtunnel
Audi's tunnel is also aeroacoustic, so you can do measurements of noise generated by wind around the car. I've tested cars in there myself, and it's pretty much silent, even with the wind doing 140kph - until you put some big bluff thing in there to disturb the wind!
Came here to write exactly that. Well done 🙏👌
@@robertpalin5878 It's the way that a microphone capsule itself responds to the wind that is the problem.
I'd guess that the reason it's quiet in there is that the tunnel itself is carefully made to be aerodynamic, to be efficient.
Looking at Jack standing next to another human (other than Robert) and especially next to an old sedan, you realise just how massive he is. A tower of a man. Really puts his back seat legroom comparisons into perspective. Thanks guys. 😊
I love that he’s properly sized. If he fits I fit.
She is shorter than average, that make Jack even bigger.
Although when he's sitting in the back seats, he's driving.
0:40 JACK: “What IS drag?”
RuPAUL: “Sit down, child, this might take some time to explain…”
😂 💄 👗 👠
😂😂😂 very good 👏👏👏
Drag Force = Fᴅ = ½𝜌𝜐² 𝙲ᴅ𝙰
(in Newtons ISO, kg⋅m/s²)
𝜌 = Density of the air (1.204 kg/m³ at 20℃)
𝜐² = Speed squared (in ms⁻¹)
𝙲ᴅ = Drag coefficient (Audi GT = 0.24)
𝙰 = Frontal Area (in m²)
haha. Also tnx @@marklonguet-higgins6041 :)
Imogen just occasionally using terminology that gives away her background as an actual aerodynamics engineer 🙂 making her the perfect choice to present this!
Great tag team by the presenters, Imogen and Jack. Another fun and informative episode.
Great episode, cannot believe this stuff is freely available on youtube. Amazing.
That’s because there are many many people who choose to pay for it through Patreon, so Robert Llewellyn has been able to grow from a one-man band 11 years ago to a whole team of professional people working on the channel, and it will hopefully reach 1m subscribers this year or early next.
I’ve been watching since the beginning, but only signed up as a patron this year. I even sit through the shorter ads to make sure the channel gains a bit more revenue (the 3 min spammy ones I usually skip, although sometimes just let them play through while I read the comments)
The debut video and early videos are always worth a re-watch, because Robert is a fantastic presenter and knows his stuff.
Great to see that you continue to emphasize the importance of aerodynamics - and great to see that it is finally coming back. I hate that something as shallow as fashion could be seen as more important than the laws of physics. Also - that classic Audi 100 was always a big favorite of mine - I was 10 years old when it was released - and the aerodynamics of it was always the key reason for me liking it. More stuff like this please!
Well said about shallow fashion - physics is far more beautiful.
True, they're not called suggestions of physics
It has never left.
@@Finnv893 - then why do we see all these brick-shaped SUVs everywhere?
@@niklaswejedal463 SUVs also have a big "A" in the drag equation. So they are a doubly bad choice for those who do not absolutely *have* to have one.
Imogen's awesome - I appreciate how she explains and summarizes these concepts.
She is clearly a great presenter but the way she was throwing the correct terminology around suggest she has a background in this area too.
Yeah she's awesome and so smart! I think she studied engineering at Oxford.
The 10 year old me fell in love with slippery aero design when the 1983 Audi 100 was introduced, not only by the cool futurist looks, but also the plain rationality of it - make the car aerodynamic and save fuel - what´s not to like? Therefore, I have been quite upset over the last 25 years as big boxy energy gulping SUV:s suddenly was the norm and aero efficiency was forgotten about. Good to finally see good old aerodynamics getting a well earned comeback! Great episode!
Just a pity the etron is so electrically inefficient, and has very poor range for the battery size.
Yes - the drivetrain efficiency is THE most important factor - and then comes aerodynamic drag.
Take a look at the Hummer EV
@@NeilBlanchard actually thats inverted, the aerodynamic drag is by far the biggest drain on the battery.
The drivetrain efficiency is over 90% in most electric cars already.
@@FreekHoekstra I am talking about the overall efficiency - if you compare EVs with ICEs, the largest improvement comes from the drivetrain, and once that is "solved", then the next biggest gain comes from aero drag.
And as was commented on, if the EV drivetrain is NOT at peak efficiency, then even the best aero drag can't salvage the efficiency.
"electrically" 🤣
Fantastic episode. The sort of science-education content that we used to get from the BBC shows like Tomorrow's World. Keep it up!
A very informative video, thank you especially to Imogen for such a clear explanation of a very complex process. More please.
Absolutely loved it, particularly Jack and Imogen presenting as a team.
Their joint, “this is Fully Charged” intro was perfect 😀
Lucid Air: 0.20
Mercedes EQS: 0.20
Tesla Model S: 0.208
NIO ET7: 0.208
Porsche Taycan: 0.22
So, Audi's still got work to do.
You should check on Aptera...
But the e-Tron GT has better design than the cars you mentioned, IMO.
Aptera: 0.13 🏆
@@eskanderx1027 Aptera is not something an Audi SUV customer will cross-shop, though. They care a bit more about staying out of hospital than being THAT greenwashey.
@@Cloxxki Composite monocoques are incredibly strong and since Aptera are yet to do physical crash-tests (simulations only to this point) your "staying out of hospital" comment is pure supposition. Let's wait until we have some facts on which we can base opinions, before making uninformed judgements.
I worked as an undergrad in a wind tunnel at the NPL at Teddington. Enjoyed it so much. The smoke only comes out when the client’s on site. It’s pretty much just because it looks cool. It serves no qualitative purpose.
But then how _do_ they visualise the flow to analyse the results? Lasers?
@@deus_ex_machina_ primarily you measure the force exerted on the test object I think. Flow visualisation is useful when you want to know WHY something has an effect though.
Interesting stuff. I'm guessing since vehicle speed plays such a large part you don't really have to focus on aerodynamics so much for a delivery truck with it's neighborhood speeds and stop and go driving. Those vehicles probably benefit more from regenerative breaking, lighter construction materials, maybe solar on their relatively large roofs.
Well yeah GM EV1 was build back in 1996-1999 and also had low drag coefficient of cd=0,186.. VW XL1 (2013-2016) had a cd =0,191..
The thing is Tesla also proved with the Tesla Semi that are a lot of areas that can be aerodynamically improved to get a more efficient range on the 18 wheeler, like cover for all wheels, slicker shape of the head-cabin, different wings under the trailer to channel & flow of the air etc..
2:02 source of the graphic should be indicated. It was taking from Wikipedia, but there is a source for that to mention.
The image is licensed as public domain, free to use for any purpose without attribution.
@@GregHassler This content is owned by the Author "TheOtherJesse". If you read: "Content in the public domain may not have a strict legal requirement of attribution (depending on the jurisdiction of content reuse), but attribution is recommended to give correct provenance."
This means it depends on the Author to ask for provenance or not. No, public domain is not automatically as you said.
But here the Author said clearly:
"I grant anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law." So, it should be fine.
Always look for the source guys.
It should be noted that CFD requires multiple dimensions of approximation to work at all. So the volume around the car is divided into millions of tiny cubes in the model, and likewise the airflow, and most critically the differential equations governing the conservation of momentum are made up of an infinite series of terms, so a perfect solution for any step is impossible to achieve, even if you could somehow start with 100% accurate initial conditions.
So the models work only with a “close enough” approach, and have dramatically improved as computers can handle smaller cubes, finer time steps, and more terms in the equations, but can never resolve everything.
Which is why engineers always end by building physical models and testing them in “real” conditions.
All the same applies to weather and climate forecasting, btw - computers are incredible, but they cannot work miracles.
CFD has a lot of limitations; witness the huge expense on simulations in Formula 1 design that still result in huge variation in car design and performance each time the rules are changed a bit. They rely hugely on testing and opex to refine things
Surely, it critically comes down to a battle between maximising aerodynamics and DESIGN!
You don't want your Audi to look-and be, completely preposterous - and, crucially, you want it to look like an AUDI!!!
@Simon de Haas - absolutely, but my point was that those limitations can only be mitigated a little with more advanced computing, because of the nature of the non-linear equations within the model. And I didn’t even go into the issues with establishing the initial conditions in terms of pressure, air density, humidity, temperature and direction.
Many people have a naive belief that we can just keep throwing computing resource at a problem and we can get “more accurate” results, but whilst we can improve the models we will never remove the need for physical models and real world testing.
Formula 1 presents orders of magnitude more difficulty to aero designers than ordinary road vehicles of course, with speeds, accelerations, decelerations and interactions with other cars all presenting huge challenges.
And I won’t say anything about the fact that some teams stretch the definition of what is allowed within the regulations 😀
I've been a convert to the benefits of reduced drag when I built my MkIII Midas Gold. Initially I drove the completed car without the under-trays fitted. When passing juggernauts there was a definite twitch felt twitch felt at the steering wheel. Access to a friend's pit allowed me to fit the under-trays. The difference was immediately noticeable, no twitch when overtaking juggernauts and the car felt much smoother. You had to watch out as it was too easy to exceed the speed limit without realising it.
Thank you, Gordon Murray for you input to the design!
All this was in 1986.
The Aptera getting 10 miles per kilowatt hour is a perfect example of how critical aerodynamics can be. (Most EVs get 5 or less, with upper 3's being the average)
You can count this Audi in the "or less category" ^^
It's a perfect example of how critical all things related to efficiency is. The Aptera is more aerodynamic, lightweight and has in wheel motors. It was designed from scratch with the idea of efficiency, not focusing on how cool it looked or making sure it had 4 or 5 seats.
..and a clear reminder that, relatively speaking and despite progress, aerodynamic efficiency at Audi (and almost everywhere) is still an afterthought.
I am really interested in the second car Aptera does which will have 4-5 seats and 4 wheels, and probably still be more efficient than the others. Rumor says they may be able to add a third seat in the smallest battery configuration of the initial car which help break it out of the niche of two seaters.
@@flannel2699 More like one important factor, next to everything else (looks, comfort, performance). Aptera can get away with their so high focus on aero efficiency because they are essentially aiming for that pretty niche market of people who are fully focused on range and low fuel costs. If Audi or other established car manufacturers would switch to aptera like designs, they'd see their sale rate plummet quite quickly. They really need to thread the needle and find the right balance between all those factors.
JACK AND IMOGEN TOGETHER?? 🤯
@ 4:40, A single cheek slide certainly minimises any friction. Even less if you clench.
Look at the distance that Imogen pulled on Jack. She can really hold a slide!
This was an extremely interesting topic. Very informative.
I'd like a Sono Sion, but can't go past the aerodynamic efficiency of the Aptera!
Excellent presentation Jack & Imogen. I didn’t realise Jack was such a heavy smoker. I sincerely hope that aerodynamics (and other disciplines) continue to improve the efficiency of our vehicles, and that cheap fuel never again compromises car design.
Worth pointing out (given all the comments below about efficiency of the Audis) that the Teslas are particularly good in their AWD versions because of their "hybrid" motor setup. They use permanent-magnet motors on the rear wheels to do most of the work, where the running efficiency of the permanent-magnet motor outweighs its relatively high running drag (when coasting, you can't prevent inducing some waste current in the coils since the magnet is always "on"). In front, they use induction motors, which are not as efficient, but have quite low running drag, since you can turn off the current that induces a magnetic field in the rotor. Then you use the permanent magnet motor in the rear to do most of the drive and regen braking (catering to its strengths) and turn on the induction motor in the front when you need AWD traction or brief acceleration (again suiting the motor to the task). Very clever, and resulting in a car like the Model Y which is AWD, but still gets hwy eMPG of 117...compared to the e-tron quattro which gets (gulp) 77 eMPG on the highway (and in the real world, highway eMPG is what most affects range for the vast majority of drivers). Design matters!
This is one of the best videos you guys have done recently. Super entertaining and all really informative!!
0:56 Hummer EV: hold my beer.
The Fully Charged videos are always well put together and presented. This one no exception and gives excellent coverage of a topic too often ignored. Thank you Imogen and Jack for making it easy to understand.
I t's about time that aerodynamics has risen to the forefront. It is also interesting, that it's AUDI that you chose to show the development of cd. Thanks
Do you mean because Audi make some of the most inefficient EVs? Or do you suspect that Audi are using this for some free advertising?
Very enjoyable and informative team ( just wanted to see them stand back to back 😁) . Interesting to see just how crucial the aerodynamics are in vehicle design now, just imagine how much gasoline could have been saved over the years if it was always applied🤔
Exactly my thoughts
Great episode. Please don’t forget the Hyundai Ioniq. A very slippery car. Drag Coefficient .24 Not the greatest looking car but very efficient.
Those big 4x4 travelling at speed on the outside lane make excellent aerodynamic wedges to follow. I regularly achieve 5.1MKwH behind them. Coaches are also good. A lot depends on how you drive. As a pilot I know all about drag and how to exploit the effects of air resistance. The difference between 65mph and 70 is noticeable. It’s about finding the sweet spot.
I suggest you produce a short with Jack (and potentially Imogen, if she was in the same position) addressing his perspective as he was operating the smoke gun and visualizing aerodynamics concepts, how it impacted his perspective.
What's missing is the consideration of the conflict between shaping the vehicle to optimize the aero and optimizing the footprint, the inner volume.
The noise treatment for the wing is brilliant, whether through the mic covers or post-prod.
Imogen did a fantastic job interviewing!
It still amazes me to see the wheels looking like big fans and most all vehicles don't cover the rear wheels all the way to the lower rim. Maybe they are saving some improvements for the next model? We know they can do better than 0.20.
So if Audi is so good with Aero, why is the Audi e-tron GT only rated at 82 mpge compared to 132 mpge for the Tesla model 3?
Spot on. Looks like Fully Charged were on a corporate jolly.
Maybe because Cd is only a one in a dozen different factors that ultimately contribute to range? Frontal area is a huge factor and he eluded to the fact that the design team wont make adjustments for the sake of aero. So corporate branding concerns outweigh efficifiency for some marques.
Maybe Audi don't want their cars to look like Tezzlers.......!!
......and who can blame them!!
The real reason is no one else bothered to give them an interview and tour, only Audi did
@@andymccabe6712 From the side, the Audi e-tron GT and Tesla Model 3 look remarkably similar.
Flat bottomed cars, you make the rocking world go round
A really great episode. Please, more informational videos like this. Thank you.
I can't understand why aerodynamics was not a priority before EVs. Why did we not add aero hub caps, retracting door handles and camera rear view mirrors years ago. 🤔
Back in the late 80s, I worked at a Subaru dealer for a while. The XT was the closest thing they had to a sports car. I can't remember what the coefficient of drag was, but I remember they were quite proud of it at the time.
Very entertaining and informative. Jack and Imogen are a great presenting team
Yes! More of them together, please. Imogen plays the straight, and Jack goofs off a little now and then. Classic!
I used to run an environmental test chamber for Esso at Abingdon, so I really enjoyed this video.
A well done exposition of a technical subject. Fun too.
It's funny considering the Audi e-tron GT is objectively bad in efficiency (202Wh/km) compared to a lot of electric cars. Hyundai, Tesla, Renault, Peugeot, Cupra, MG... All achieved 160-170Wh/km on similar sized cars. It goes to show how much the industries values this kind of testing, it's really one of the keys to making great electric cars.
I've been driving for a number of years, and my four favourite owned cars from yesteryear were a Citroen GS, an Audi 100, and my absolute favourites, my two Saab 900s. One an Injection, one a Turbo 16. All the cars had aerodynamics high on their list of priorities. All through those times I had been waiting for battery technology to catch up to the electric motor. These days, it's a VW ID.3. Maybe the next one is a Tesla. I love not having that unnecessary front grille that causes drag.
Such a pity that cars look so utterly ridiculous without a grill!
Kinda like Lord Voldemort........!!!
If you stare at the 'nose' of a Tezzler for any length of time it gradually morphs into something really quite scary.......
@@andymccabe6712 But they look even worse when they have one but don't need one. And I've never heard any adverse comments of Porsches and VWs with rear engines and no grilles. You get used to these things.
Glad to see a focus on efficiency on this channel, Its the fastest way to get more range for less cost and is more interesting and useful than how fast a car gets from 0 to 60.
I want to know how fast Ev's can get from 500km of range to a 1000km for under 30 grand, now that is a metric worth knowing about.
They probably get there by having gigantic batteries. Big, heavy EVs like that are not a good idea in my opinion. They’re much heavier than their ICE counterparts that have similar or greater range, which is worse for the road infrastructure and worse for pedestrians and other road users in the case of accidents. A small, light EV with a small battery that provides modest range along with a larger ICE car for longer journeys would be a better combination for most families.
The sweetspot is a EV w/ 25-40kwh battery that gets 150-200 mile range but only costs $15-20K USD. No autonomous driving, no amazing 0-60 times just simple & reliable & efficient. Basically a model 3 without the tesla brand & gadgets
Glad to see the photo of a 1960 Ford Thunderbird. The 1958-60 T-birds were nicknamed “squarebirds.”
the answer to why you need a wind tunnel is to ensure that the computer flow simulation is accurate. Most flow simulation software uses particle emission simulation and a series of complex predictive algorithms to try to determine how the forces will load on a surface, and thus help to determine what the coefficient of friction and, thus, drag should be for a vehicle. But, because the sample size is somewhat low due to processing constraints and the algorithms can't perfectly represent reality, it is still necessary to build a model and chuck it in a wind tunnel to validate their predictions from the 3D computer model.
So, it isn't that we can't simulate it, because we can. It's just good to acknowledge that our simulations still aren't quite up to the high bar that is reality.
Quality geek TV - Great combo with two presenters who have a genuine passion for the subject. I feel like there's been another move forward of late, keep it going 👍
Very interesting watch!
But the market pushes companies into building SUV. A brick on wheels (with a bit of smoothing sure).
Right now, I'm guessing if you gave people the choice between an electric A4 or an electric Q4 the latter will probably sell better.
It's a hard task making a car as aerodynamic as possible within the market demand (like the car sizes, preference to regular mirrors and handles, etc).
You know what? I really like the Audi E-Tron shown here, however, I am too infirm to get into it without pain, and getting out is more difficult. So, for those who keep bashing and decrying the SUV style electric cars, have a thought for those of us who need to be able to get into our car without having to suffer for it. Once in, maybe the many thousands of people like me get comfortable, but dread getting out of the car. For me, this is important to have a higher car to get into easily. Up to now, it's the SUV, in the future, there may be something better that does not offend people because of its size.
@@BobH809 But by using an SUV, sitting in high chairs etc. you're only exacerbating your frailty.
Edit: This didn't come out right, what I meant to say is that just like the higher bumper height of SUVs and pickup trucks necessitates ever more massive vehicles, similarly insulating yourself from the least bit of discomfort only makes it harder to function normally.
It's a race to the bottom, basically.
@@deus_ex_machina_ So, you're saying I should just suck it up, suffer the pain and discomfort and get a normal car?
@@BobH809 Well, I realise how it came off that way, but no, I'm emphasising the importance of functional movements in daily life, basically turning normal activities into physiotherapy.
Upright Health's channel and Not Just Bike's video on 'The Gym of Life' are examples of the philosophy I espouse.
@@BobH809 Oh for sure I would never disparage someone's choice due to infirmity. To me the general market demand does not include ppl with disabilities or other difficulties. I'm guessing most SUV buyers do not get their car because it would be genuinely giving them pain if they didn't.
Excellent reporting, thank you
Filming in a wind tunnel with no background wind or machine noise. What magic was cast to do this?
FFT noise reduction in Audacity.
@@arijarmala2037 Wow. What a time to be alive! Thanks.
Excellent mic placement, and voice isolation
@@fullychargedshow Well planned. I'm watching the hair blow around but not a sound other than voices.
Great episode, Jack and Imogen make a great team. More of this please. Comparing your gait on sprinting back up the slope, Imogen clearly has a much lower Cd (not to mention CofG) than Jack. 😊
also Imogen's leggings have great drag coefficient. 😀😀
@@johnsmith-cw3wo I doubt that they’d fit Jack ?
No need to shill for Audi, Saab was the leader of the aerodynamic revolution in regards to cars, windtunnel testing since forever
Brilliant video, nicely presented and really interesting to see where the future is heading. Cracking car as well, look forward to collecting mine soon once production delays are sorted.
Great video guys, really informative! Please keep them coming :)
For air density, you need to know the temperature, the altitude, the humidity, and the atmospheric pressure.
Cooler air is more dense than warmer air.
Air is "thiinner" at higher altitudes than it is at lower altitudes.
Higher humidity air actually has *lower* density - which is counterintuitive, but it is.
Atmospheric pressure varies, but this is probably the least critical factor of these.
Below 250MPH, lower drag shapes have a *blunt* front end - and a pointy back end. This is because most of the drag is generated *at the back* of the vehicle. A low drag shape lets the air close back in behind the vehicle has pushed through - with as little turbulence as possible.
What I want to know is to quantify what a reduction in drag does to the range, so what’s the difference in range between a car with a drag coefficient of 0.3 and 0.24
Really great lesson in car design from 2 excellent presenters. If only I could afford that Audi...
7:25 I guess the rain was always teaching us what the most aerodynamic shape was
Ok, I'll be the weirdo:
Slippery when designed well...
And I loved the design.
Excellent video! Glad Audii is helping explain the concepts. More companies need that than look at how big a boat you can tow!
Excellent episode, very informative and great to see these facilities in action! Also, the team-up between Imogen and Jack works really well 🙂
Small gripe though: OK to use "handwritten" text in the graphics, but is it necessary to keep them wiggling all the time?
Wiggles are all the rage these days...
We have a very nervous animator
I think frontal area is heavily overlooked. My boxy, non aero, brick of a windcatcher: an old Citroën 2cv (0.51) has the SAME drag as a shape optimized, windtunnel tested, Tesla model X (0.24). This is completely due to the fact that the model X has over twice (!!) the frontal area of that inefficient shaped car of mine. Let's make cars small and sensible again! The model X mini would be twice as efficient (and no, the y doesn't count, it's still slightly massive)
I remember a Dinky toy model of a land speed record car called the speed of the wind. If you look at many of the current designs they still show the same principles.
Wow... I hadn't thought about Dinky Toys since I was a kid. I used to love them. I think I still have a few in a box in the basement. They were made of metal with real rubber tires, so that last just about forever. Thanks for the memory! ☺
Excellent insight into an aspect of car manufacturing that we rarely get to see.
It's great to see someone as informed as Imogen do the presenting...you can tell from the way she seamlessly talks about nice laminar flow and separation she knows her stuff. So ironic that the company willing to host was Audi, whose EVs are utterly at the bottom of the pack when it comes to efficiency (eMPG). Perhaps they were hoping to use this forum to distract from that fact?
I remember speaking to someone in the late 80's who had been involved in some sort of auto racing. This man had absolutely no concept of drag or the drag coefficient formula. He adamantly believed that the only thing limiting a car's top speed was the gear box and the amount of straight track available. I was appalled.
Thanks Audi for showing us. Thanks FC for making the movie. Please reduce the squigglyness of the crayon font.
Good explanation and graphics!
Another great episode guys! Imogen explains the concepts so well.
Thanks team, we need more videos like this. The etron is not an efficient vehicle and has poor range.Mass and electric efficiency carry as much "weight" as CD. 2 examples; Aptera /mass 800 kg CD 0.13 700-1600km range (solar) Ford F150 Lightning/mass 3tons CD 0.56 range up to 500km /towing 200-250km (estimates). PS; this episode reminds me of Beyond 2000 and Tomorrows World.
12:06 0.24 right around (15-year-old) gen2 Prius cD.
Imogen & Jack make an incredible team for presenting this sort of scientific knowledge & artistic awesomeness, great episode 😄🙏🏼 Aerodynamics is cooler than I previously imagined 💚
I got to say “well, we are in Germany, it would be rude not to” for almost 17 years on and off, living in Hannover, Bergen, Bielefeld and Gütersloh. If certain obstacles were removed I would do my best to go back.
As a student of computational science master program , I find it fascinating
Like your phone. The most important part is battery degradation. Nio does battery swapping stations so you constantly have a new full battery within minutes
How low can we go? Well if we start ditching the old brick shape we've been forced into we can go a lot lower - low 0.10s...
Just a killer video, well done.
I had an Audi 100 avant, even the car jack was aluminium. I had the 1.8 carb model and could get 42mpg fully loaded for camping
Nice one peeps, and Jack if Imogen wants to go for a beer, you say yes ma'am!!
Yeah, but science can't explain how a human camera operator managed to fit Imogen and Jack into the same shot.
Jack has a very interesting way of saying 'slippery', and he seems to like using the word too!
Packed with great information leading into the upcoming generations of vehicles.
hi ryan
Great video !! Hope SUV's owners see it ! What's the use of electrifying 2 to 3 tons-heavy bricks ? ( do you hear me BMW/ Hummer/ GM etc etc ...of course you don't ahaha !) ??? Also hope the trend will change and people understand that our cars will need to look as much as possible like the APTERA or the Mercedes EQXX ;). Thanks for your videos !!! Bonne journée !
Such a great video - many thanks to all involved!
Worth considering velomobiles here. So aerodynamic, and so much lighter than a car, that they are around 80 times more efficient than a Nissan Leaf !!! And that means 1/80 of the cost to charge up.
It's amazing how aerodynamic features like wheel covers, undertrays, flush door handles and camera mirrors aren't more common on ICE cars. They would benefit*more* in terms of energy costs and emissions reductions in absolute terms than EVs do.
Possibly true, but the auto industry has grown fat on historically very low fuel prices, and people have got used to driving hulking great bricks around without giving a feck about it. That has changed only recently, but any car maker investing in new ICEVs is going to waste a lot of money, when their sales are dropping exponentially.
18:07 Logitech mouse from the early 2000s, I love how Audi are using bleeding-edge tech. ;)
Citroen we’re obsessed with aero since the 1950s. Cars like the GS had, for the time, excellent figures as low as 0.30 CD…
The same tricks work for ice cars just as well for more mpg.
In response to your question, I once owned an Audi 5000 estate, one of the best cars I've ever driven, slippery too.
You guys do such a good job. This was a very fun and informative video. Thank you.
Question regarding your drag coefficient data. What is the A (area) used in the formula to calculate the drag coefficient?
After all, we ar interessed in the lowest force being created when comparing cars :)
"A" = frontal area measured in square metres. If the front were rectangular when viewed from directly ahead (disregard the visual-perspective aspect of it), it's the width x height. With an irregular shape (which is more commonly the case), you have to do the math but it amounts to the same.
Cd gets multiplied with A. Which is why I always find it funny, when people congratulate HUGE cars with record-breaking Cd-values, when a small, less aerodynamic car will run circles around the big one, just because the frontal area of the whole box is half of the big car. Squeezing the last 0.01 Cd out of a car is nice and all, but buying a car which is 20cm slimmer will fix that manyfold.
Fantastic episode. Really interesting. Loved it.
Aerodynamics are so crucial yet manufacturers insist on producing wardrobes on wheels, gunging great SUVs looking like they were chiseled out of granite. The Toyota Bz4x being a prime example.
The great advantage of EVs over ICE vehicles is the flexibility of design that is possible. In an ICE vehicle you can't get away from certain structural requirements of having to using an engine, a clutch assembly, a gear box and a fuel tank. In EVs you can have a motor in the front, in the back or both. You can have two motors, three motors or four motors as standard. You can have the motors inside the wheels. You can have the motors front mounted, centre mounted, rear mounted or any combination of the three. And the same is true of batteries. They can be placed anywhere that there is space and can be used to change the cars balance and even be part of the structure.
What's this got to do with aerodynamics? Well, if you remove most of the limitations of how you design a car by making the positioning of the "fuel" and the location of the traction device[s] (motor[s]) infinitely more flexible you can avoid the blocky, bulky, inefficient shapes that were once necessary to house the bits that make a car functional. The greatest current example is the Aptera Gamma. With batteries between 23kwh and 100kwh in size the streamlined build allows for 10 miles per kwh economy. Therefore even the 23kwh car can run for 230 miles. When my 2015 24kwh Leaf was manufactured it was advertised at 80-90 miles of range which maxes out at 4 miles per kwh. In actuality it was quite capable of 110 miles of range (4.9 miles per kwh) in normal use. Just seven years later and the Aptera can go more than twice that distance on a smaller battery. It's largest battery allows 1000 miles of range. With the addition of solar charging you may find that you don't have to charge the car for months at a time as it will acquire more energy sitting in the sunshine for a day than most people will use in a normal day. Therefore, it has surplus power that means the battery can be fuller every day than it was the previous day without having to plug it in at all.
But, back to the plot. The aerodynamics of EVs have more potential than ICE vehicles because of the mobility of the components within the structure. If you want a Bugatti Veyron you just have to concede that it's going to have an enormous engine, a huge fuel tank, a clonking great gear box and chunky clutch assembly. That is going to be fitted into a frame that is built as a compromise between containing those elements and streamlining the shape. The original Bugatti Veyron had 1001 horsepower. It would use the first 250hp to get to 150mph. It took that much power to push it through the air. But, it then needed the next 751hp to reach 252mph. For stats nerds that means it averaged 1.67hp for every mph up to 150mph, then averaged 7.36hp per mph for the next 102mph. This is because it's aerodynamics were dictated by it's need to house necessarily bulky components. EV design minimises this issue. And as batteries achieve higher energy density the volume needed for any given capacity decreases. Look at the Renault Zoe. It went from 22wkh to 41kwh to 52kwh in six years while retaining the same battery volume.
Just more evidence that EVs are the future and technical evolution in transport no longer requires the presence of fossil fuels.
American car designers: Interesting.... Now, if we wanted to do that, but with a vehicle about three times larger shaped like a big box....
Great work guys - Really interesting piece. I wonder how the same challenge looks for the world of vans, that are a way behind in the aerodynamics department... I think the Brick was most appropriate!
Details matter. For example, Fiat Ducato (sold as Ram Promaster in North America) Cd = 0.31, which is rather surprising for a vehicle of such a shape. Obviously someone paid attention when designing that one. The problem, of course, is the frontal area. A great big box that someone can stand up inside, there's only so much that can be done.