## The return of wind powered vessels

 

### Ship aerodynamics

Large vessels have been sailing our oceans for many centuries, transporting goods to all parts of the world. They were, in their beginnings, solely powered by wind, which made the success of their journeys highly dependent on meteorological conditions. With the industrial revolution, engines were developed and introduced into these vehicles to provide a more reliable constant source of power. Two centuries after the first steam-engine sailed the seas, an excess of the use of fossil fuels is forcing this generation to come up with innovative ideas that will allow world-wide transportation to be continued but with a reduced carbon footprint. It is in the amidst of this necessity that the <ExternalLink href="https://www.oceanbirdwallenius.com" >Oceanbird</ExternalLink> is born, a joint project between <ExternalLink href="https://www.walleniusmarine.com" >Wallenius Marine</ExternalLink>, the <ExternalLink href="https://www.kth.se/en" >KTH Royal Institue of Technology</ExternalLink> and <ExternalLink href="https://www.sspa.se" >SSPA</ExternalLink>.

### Dr. Laura Marimon Giovannetti

For this blog, we have interviewed Dr Laura Marimon Giovannetti, who is working at SSPA as a senior researcher. Prior to moving to Sweden, she spent many years at the University of Southampton in the UK, where she studied and completed her PhD and a postdoc. During her PhD, she was be able to work in the design team of the British Challenger for the 35th America’s Cup (Land Rover Ben Ainslie Racing). <Link href="/blog/sailing-yacht-aerodynamics-and-hydrodynamics">Learn more about sailing yacht aerodynamics here</Link>.

<ImageWithCaption
 src="/assets/images/profile-picture-laura-marimon-giovannetti.jpg"
 alt="Dr. Laura Marimon Giovannetti"
 width="400"
 height="400"
/>

Alongside her whole professional career, she has also been an elite athlete in sailing, representing Italy and then the British Sailing Team at World and European championships. She shared with us that her knowledge of sailing as an athlete as well as an engineer has definitely helped her shape her path in high-performance sports and now also in wind propelled vessels. "The latter especially reflects not only my passion for sailing but also my personal involvement in sustainability, as I would really like to admire the sea that once again is used to transport goods in a clean and sustainable way".

<YouTubeEmbed
 videoId="pZVDs4n_a0M"
 imgSize="default"
 title="The Wallenius Marine Oceanbird"
/>

## Wing sail design

### Airfoil sections

The wing sails are essentially aerofoil sections. Contrarily to aeroplanes that only need to create lift in one direction, in a ship the wings would need to create lift, or side-force in this case, in both left and right direction, commonly defined in a marine environment as port and starboard, respectively. It is therefore evident that ships are not actually able to sail straight against the wind. Therefore, the wings need to rotate independently to achieve the best combination of overall aerodynamic drive to allow the ship to move forward. The wing sections also need to be symmetrical to sail both directions – or tacks. Moreover, contrarily to an aeroplane where you would have a main wing of long span and a short rear tail wing, in the Oceanbird the wings are all of the same size and it is extremely important to understand the interaction effects that would change the overall drive created.

<ImageWithCaption
 src="/assets/images/oceanbird-top-view.jpg"
 alt="Top view of the Oceanbird sails featuring a symmetric airfoil section - Image credit: Oceanbird"
 width="1000"
 height="562"
/>

### Aerodynamic interaction

Aerodynamic knowledge is key when we start talking about interaction effects between the wings. Indeed, we need to understand that if one wing produces a certain amount of lift, the interaction between that wing and the one behind or in-front will change the overall lift created. Another effect of interaction is seen on the effective angle of attack or stall angles as the wind bends around the front wing to then reach the ones behind.
Other aerodynamic knowledge comes to our advantage when we want to design the top part of the deck. As the ship travels forward, the wings, which are sitting on the top deck, are affected by the superstructure. So, investigating new deck designs is key to achieve a consistent flow direction avoiding aerodynamic losses in the lower part of the wings.

### The tallest sails in the world

The largest wings built at the moment are for the F50, a high-performance sailing vessel racing in the Sail GP circuit. The main difference is the necessary drive force to move forward a heavy car-carrier compared to a relatively light sailing boat. Current wings for sailing boats are optimised on a vessel mostly made of carbon fibre, that has a very high stiffness to weight ratio. Traditional commercial ships are instead made almost entirely in metal and are undergoing strict safety regulations, so the overall weight is brought up to be able to withstand all the necessary loads. The wings in Oceanbird are therefore designed as tall to be able to drive forward a commercial vessel around a specific route always maintaining a minimum speed to be able to deliver the goods in time.

<ImageWithCaption
 src="/assets/images/oceanbird-tall-sails.jpg"
 alt="The Oceanbird sails will reach a height of 105 meters above the waterline - Image credit: Oceanbird"
 width="879"
 height="1080"
/>

### Telescopic sails

“Reefing the sails” is a normal manoeuvre in sailing. It is necessary to reef the sails, effectively reducing the surface area of the wings, when the side force generated is too large due to strong winds. In those conditions, as the side force is acting at the centre of effort of the wings, so approximately at half-span, the heel moment becomes too large to sustain safely and without causing damage to the content of the ship and the crew. Therefore, we need to lower the wings down to deck level to lower the centre of effort, still being able to produce drive force but in a much safer way. The possibility of reefing the wings and lowering them completely to the deck is also important in in-port operations and when we encounter bridges en-route.

### CFD simulations on sails & ships

<ImageWithCaption
 src="/assets/images/oceanbird_cfd_1.jpg"
 alt="CFD analysis of the sails - starboard view (note the wing tip vortices) - Image credit: SSPA Sweden AB"
 width="1000"
 height="590"
/>

In our partnership between Wallenius Marine, SSPA and KTH we use a large number of different design approaches, varying from low-confidence to high-confidence levels. The higher the confidence level grows (i.e. moving toward wind tunnel tests or accurate CFD modelling) the higher the costs involved and the time to get the results. So using a combination of different fidelity models is key to a successful design spiral.

<ImageWithCaption
 src="/assets/images/oceanbird_cfd_2.jpg"
 alt="CFD analysis of the sails - port view - Image credit: SSPA Sweden AB"
 width="1000"
 height="590"
/>

### Wind conditions.

The sail rotate independently to be able to provide aerodynamic drive in all conditions, aside when heading directly toward the wind. There is an area of plus-minus 30 degrees of true wind angle that in sailing is a “no-go” zone as the ship is not able to sail directly toward the wind but is instead using a zig-zag approach to sail toward the wind direction.

### Environmental break-even

We’re currently working with material selection and production techniques for the wing sails, for example investigating the possibility to use recycled composite materials. It is therefore at this phase too early to state the break-even period (the time needed to save as much CO2 / energy as was needed to build the ship in the first place).

## The future of wind powered shipping

<ImageWithCaption
 src="/assets/images/oceanbird-front-view.jpg"
 alt="The Oceanbird - the future of shipping? - Image credit: Oceanbird"
 width="1000"
 height="562"
/>

### Sails versus kites

Kites are very large soft-sails that are deployed in certain wind conditions. They are mostly efficient at “pushing” the ship forward when the wind comes from behind. Our wings instead work producing lift, like aeroplane wings, so their preferred angles of attack are lower, below stall.

### Future challenges

One major challenge that we face is to prove the concept and the possibility of effectively reducing to a minimum the fuel consumption. Being able to do it will create a positive movement where we can prove that even with wind powered ships we can deliver goods across the world in time. Another important point is crew training for the new systems onboard.

### Scaling down

There are some projects currently looking at small passenger ferries that could be fitted with sails. I believe that once we have proven the concept and we will be sailing with the Oceanbird then more projects will follow!

### The first cross-Atlantic journey

The target launch for the first Oceanbird concept (the Orcelle), which is currently under development together with Wallenius Wilhelmsen, is 2024/2025.

Interesting links:

<ExternalLink href="https://www.oceanbirdwallenius.com">Oceanbird</ExternalLink>
 

<ExternalLink href="https://app.airshaper.com/projects/new?accuracy=regular">
 Run Your Own Simulation
</ExternalLink>

The Oceanbird Wind Powered Vessel

## What is vehicle water management? 📢

When was the last time you saw the message ‘clean me’ on the back of a dirty car, truck or lorry? If it’s winter where you are, then it probably wasn’t long ago. But why do some vehicles seem to get dirtier than others? Ok, some owners are not the best at keeping their vehicles clean, but aerodynamics also has a major role to play.

To find out the physics behind vehicle water and dirt management and how simulation can help, we spoke to our two partners <ExternalLink href="https://www.nextflow-software.com/">Nextflow Software</ExternalLink> and <Link href="/partners/engineering/a2mac1">A2MAC1</Link>.

### What is vehicle soiling?

Water management is a huge topic. It encompasses everything from designing efficient windscreen wipers to adding aerodynamic devices to control the exterior airflow around a vehicle.

‘It’s essentially all about the interaction of liquid with the exterior surface of the car,’ explains Vincent Keromnes, Dynamic Benchmarking Domain Leader at A2Mac1. ‘This can include rain, water wading and water injection. It’s crucial to monitor where water can get through on a vehicle. If it accumulates in the engine bay, battery pack or on a camera, it can cause major issues.’

It’s not just water that’s a concern though. Dirt, debris, stones and other particles also need to be monitored. Due to the miniature nature of these particles, they are strongly affected by the behaviour of the exterior airflow. Therefore, the aerodynamics need to be designed to minimise these particles either hitting the surface or being ingested in intakes and openings.

‘There are two main sources of soiling,’ highlights Keromnes. ‘Firstly, there is self-soiling which is from the vehicle itself. Wherever there is flow separation, such as on the sideview mirror or at the rear of the car, a wake is generated which causes contamination. Then there is third party soiling which is caused by the interaction of wind, rain and dirt with other obstacles on the road.’

**Did you know?**
The bigger the rear wake of a vehicle, the dirtier it will get. This is why SUV’s get dirtier quicker than other types of cars - because it has a much larger wake. <Link href="/blog/mercedes-eqc-drag-coefficient">Find out why SUV’s aren’t aerodynamic here.</Link>

<ImageWithCaption
 src="/assets/images/SUV-rear-soiling.jpg"
 alt="Accumulation of contaminant on the rear of an SUV after 75 s, obtained using a UV fluorescence method in the FKFS thermal wind tunnel - Image credit: FKFS / Adrian Gaylard"
 width="640"
 height="480"
 positionCenter={true}
/>

### Why is vehicle water management important?

We all like to see where we’re going when driving, no matter what the conditions are outside. If you’ve ever experienced a faulty windscreen wiper on a motorway, then you’ll have a particular appreciation for this.

‘The most important reason is obviously safety,’ explains Keromnes. ‘Drivers have to have clear visibility through the windscreens, windows and side mirrors, so avoiding dirt deposition on those areas is critical.'

'Also, with more ADAS systems onboard modern vehicles, cameras and LIDAR sensors are very sensitive to dirt. Just a droplet of water on such a tiny camera can seriously affect its performance. This is becoming increasingly important as we move towards more autonomous driving. These types of devices need to stay clean or be easy to clean.’

<ImageWithCaption
 src="/assets/images/tesla-sensor-locations-small.jpg"
 alt="Tesla Model 3 sensor locations - Image credit: System Plus Consulting"
 width="640"
 height="406"
 positionCenter={true}
/>

‘Aesthetics are also a part of it. This is why some manufacturers develop their designs to drive soiling into areas that are not so visible. There’s also the comfort side of things. You can imagine if you’re a truck driver, you don't want to get covered in dirt every time you grab the door handle.'

### How do manufacturers manage dirt and water?

Dirt and water management are a key consideration when designing a vehicle’s exterior. Early in the design process, designers analyse the vehicles aerodynamics to control the behaviour of water and dirt to keep key areas of the vehicle clean. However, in areas where this can’t be done, engineers have to develop systems that remove dirt and water.

‘It’s difficult to find an area on a car that stays completely clean. Sometimes your only option is to put a cleaning system in place,’ says Keromnes. ‘That’s why in the 80s and 90s Mercedes cars had a wiper system on the headlamps.'

'As well as wiper systems, carefully controlled spraying techniques can also be used which are efficient and inexpensive. This has become so important that some manufacturers now have specific departments dedicated to developing these spray systems. It's interesting to know how fast a car can get dirty, but it's also interesting to know how fast you can clean it. Both of these can be done through simulation.’

### How do you simulate the flow of water and dirt particles?

Accurately modelling the behaviour of a consistent airflow over a vehicle is challenging enough. Add in the effect of wind, the dynamics of water and the trajectories of dirt particles, and you can begin to appreciate the difficulties of simulating water and dirt.

This is why such analysis requires the combination of aerodynamic and hydrodynamic simulations. As the water droplets on the vehicles surface are so small, these local flow fields don't have a major effect on the vehicle’s aerodynamics. Therefore, computational fluid dynamics (CFD) simulations evaluating the global aerodynamic performance of the vehicle are completed first. Then, this flow field is used for separate simulations where liquid particles are injected into the simulation to predict the forces and trajectories of water and dirt particles.

<YouTubeEmbed
 videoId="VYQkWA2MWj0"
 title="Sensor Soiling Analysis on a Model Y 3D scan"
/>

‘If we need to conduct a more detailed analysis we can also add in some particle refinement algorithms. This allows us to evaluate the wettability effect such as surface tension, dynamic contact angle etc of smaller particles in more specific areas,’ says Julien Candelier, the technical team leader at Nextflow Software.

Of course, such complex simulations require a substantial amount of computing power. ‘The main challenge is memory management,’ highlights Candelier. ‘That’s why everything is modelled as a steady flow using a mean value of diversity of car wake. Even with that we are dealing with gigabytes of data.'

'To cope with this, we do some parallel computing for the liquid phase to achieve efficient simulations. For example, a full wheel soiling simulation can run in 20 hours on a regular desktop.’

The ability to accurately model liquid flows quickly and efficiently means that these simulation techniques can also be used for other flows within a vehicle. For example, e-motors can rotate up to 15,000rpm, generating airflows that can significantly effect oil flows within the transmission.

<ImageWithCaption
 src="/assets/images/gearbox-lubrication-simulation.jpg"
 alt="Gearbox lubrication simulation - Image credit: Nextflow Software"
 width="477"
 height="424"
 positionCenter={true}
/>

‘We use the same technology to study the cooling and lubrication performance of rotating gearboxes,’ reveal Candelier. ‘Using a similar approach, we assume the oil flow doesn't influence the overall airflow, but the airflow does influence the oil flow.’

‘A Formula E team used our software to investigate a gearbox issue where the oil temperature was rising by 1degC or 2degC per lap. The engineers were able to reproduce this phenomenon with our software, test, validate and develop a new design which solved the issue.’

So, next time your car gets dirty – just think how many more times you would have to wash your car if it wasn’t for simulation.

Interesting links:

<ExternalLink href="https://app.airshaper.com/projects/new?accuracy=regular">
 Run Your Own Simulation
</ExternalLink>

 

<ExternalLink href="https://portal.a2mac1.com/">A2MAC1</ExternalLink>

 

<ExternalLink href="https://www.nextflow-software.com/">
 Nextflow Software
</ExternalLink>

Vehicle Water Management

## Ever wondered how the drag coefficient changes when you drive an SUV backwards? 📢

Imagine you are the project manager for the exterior design of the new Mercedes EQC electric SUV. Your job is to balance what designers want (an aesthetic car) with what engineers want (an aerodynamic car).

For months you have been running a variety of wind tunnel test programmes. You've experimented with aerodynamic tricks such as active grille shutters, specialised wheel hubs and smoother underfloors. All with the aim of optimising that vital Cd value.

By the end of the programme, the Mercedes EQC <ExternalLink href="https://airshaper.com/videos/what-is-a-drag-coefficient/bEgoZ_dAg7o">drag coefficient</ExternalLink> is 0.27 - bring out the champagne! However, the marketing department want to complete one last run, with two dogs in the vehicle. Well, they need marketing material and if this engages audiences then why not.

<ImageWithCaption
 src="/assets/images/mercedes-eqc-dogs.png"
 alt="Mercedes Wind Tunnel Test with Dogs - Image credit: MERCEDES BENZ"
 width="898"
 height="504"
/>

## The real joke: reverse aerodynamics

But then the real prankster of the team decides to take it a step further. He wants to run the car backwards too. Not entirely sure what that will achieve, but again – why not? It’s been a long day.

As the dogs begin enjoying themselves, the Cd value appears on the screen. It is only 7% higher than the original Cd value of 0.27. To add insult to injury, the prankster removes the rear spoiler and rear wind deflectors. The Cd value this time is exactly the same as when the car drives forwards. Time to put the champagne away.

Of course, (apart from the dogs) this is a hypothetical story. However, Vincent Keromnes of <ExternalLink href="https://portal.a2mac1.com/">A2MAC1</ExternalLink> did complete these tests virtually using the AirShaper platform. Using a high quality 3D scan of the Mercedes EQC, Vincent ran a series of AirShaper simulations with the car in reverse.

<ImageWithCaption
 src="/assets/images/mercedes-eqc-aerodynamics-backward.png"
 alt="Mercedes EQC in reverse (configuration 1 - original car) - Aerodynamic Simulation by AirShaper (pressure clouds shown)"
 width="1174"
 height="387"
/>

## Matching the original Mercedes EQC Drag Coefficient

Interestingly, the result was a minor 7% increase in drag coefficient. Vincent then wanted to see how close he could get the drag coefficient in reverse to the original Cd value. He removed the rear spoiler and the rear wind deflectors as these were significantly affecting aerodynamic performance. He then repeated the simulations and astonishingly, achieved the same drag coefficient.

<ImageWithCaption
 src="/assets/images/mercedes-eqc-aerodynamics-backward-modified.png"
 alt="Mercedes EQC in reverse (configuration 2 - rear spoiler and wind deflector removed) - Aerodynamic Simulation by AirShaper (pressure clouds shown)"
 width="908"
 height="285"
/>

## The real message: traditional SUV shapes simply aren't aerodynamic

This may have started as an amusing story, but the underlying message is extremely important. The long nose and bulky rear end of modern SUV’s is the exact opposite of the typical aerodynamically efficient teardrop shape. A good example of this is the <ExternalLink href="https://airshaper.com/videos/lowie-vermeersch-2-the-lightyear-one-solar-car/TKHjyC_L0OM">Lightyear Solar One</ExternalLink>. Despite the Mercedes EQC being electric and therefore benefitting from the packaging opportunities of batteries and electric motors. Its shape remains bulky and far from aerodynamic.

The question is why? Of course, the long nose houses the crash structure and the appeal of SUV’s is that they are spacious and comfortable. But the simple fact is that SUV&#39;s are not aerodynamic.

It seems that to ease the transition from internal combustion vehicles to electric vehicles, manufacturers are developing cars that look exactly the same as their predecessors. So they are missing out on potential opportunities to improve aerodynamic efficiency. Yet, if the aerodynamic performance of a vehicle is improved, it requires less energy to travel the same distance.

If manufacturers want us to take their claims of developing greener vehicles seriously, they need to step away from these traditional SUV shapes. Instead, they need to deliver vehicles which maximise efficiency, to minimise the amount of energy these vehicles consume. That&#39;s the definition of a true environmentally friendly vehicle.

Interesting links:

<ExternalLink href="https://app.airshaper.com/projects/new?accuracy=regular">
 Run Your Own Simulation
</ExternalLink>

 

<ExternalLink href="https://portal.a2mac1.com/">A2MAC1</ExternalLink>

The Case of the Mercedes EQC Drag Coefficient

## About the Author 📢

James Aarestad, the owner of [Eagle Eye Photography](https://blimpguy.com/), is busy building a variety of camera pods for aerial imagery on manned aircraft. His business specializes in helping his customers obtain information from the air using a variety of unique cameras attached to aircraft. And with aerodynamics being crucial to the performance & safety of aircraft, the effects of objects attached to the outside need to be checked properly.

## Finding Gas Leaks

Every day, pipelines around the world carry natural gas through millions of miles of pipe. Many people take for granted the complex infrastructure in place to route natural gas to homes and businesses for heating. As these pipelines age, small gas leaks can develop and go undetected for years. As this impacts the environment, safety and profitability, detection of these leaks is crucial.

## Specialized cameras

So the gas and oil industry needed a better way to find these leaks - one that would be flexible and efficient enough to inspect the many miles of pipeline that often cross rough & remote terrain. That's why in 2019, I began work on a camera pod that would detect these dangerous natural gas leaks from the air. This required the use of an extremely specialized camera. This camera is heavy and large, making it a challenge to attach to the exterior of an airplane. As you might imagine, attaching camera systems to Cessna aircraft is no easy task.

<ImageWithCaption
 src="/assets/images/camera-pod-aerodynamics-6.jpg"
 alt="The Eagle Eye Camera Pod attached to the fuselage of a Cessna"
 width="1323"
 height="361"
/>

## Camera Pod Aerodynamics

Our biggest design hurdle was keeping the aerodynamic footprint as small as possible. This was critical not only for aircraft control but also for certification requirements. The Federal Aviation Administration in the USA has strict regulations that must be following when modifying an aircraft and this includes aerodynamics.

We used the AirShaper platform to determine how much wind resistance the camera pod would generate at various speeds. Using this data, we were able to adjust the size of the camera pod for optimal performance. The data helped us determine the maximum allowable airspeed the pilot could safely fly with the camera pod attached. The reports helped confirm our engineers' aerodynamic estimations and helped us with certification requirements.

<ImageWithCaption
 src="/assets/images/camera-pod-aerodynamics-5.jpg"
 alt="AirShaper CFD Analysis of the Camera Pod - 3D Streamlines"
 width="953"
 height="767"
/>

## The Future

We are currently working on two more camera systems which we'll of course subject to aerodynamic analysis again. With each iteration, we'll be able to reduce the aerodynamic loads for a given camera size (reducing the drag coefficient Cd).

Interesting links:

<ExternalLink href="https://blimpguy.com/">Eagle Eye Photography</ExternalLink>
 

[Running your own simulation](/videos/how-to-run-an-aerodynamic-simulation/O_DNDxCtI_I)

Camera Pod Aerodynamics

## 📢 About the author

Lluis Vazquez Vilamajo has been a rally fan since 1978, intrigued by aerodynamics since the 80's and runs the website <ExternalLink href="https://www.wrcwings.tech/">WRC Wings</ExternalLink> since 2016:

_WRCWings is a non-profit initiative created to contribute to the understanding of the aerodynamics of current WRC cars, from rally fans to rally fans. At the same time, it is an opportunity to review the aero and the performance of some of the most iconic cars in WRC history of the last 60 years. But it also intends to recognize the effort, time and resources of so many people, teams and manufacturers to improve the aero and performance of those wonderful cars._

Note: this article is based on a much longer article at WRCWings and was (re)published with their permission. See the links at the end of this article to read the full article.

## ▶ Introduction

At a certain point in time in WRC history, manufacturers realized they could make a substantial difference through aerodyanmics. Ever since, they have been taking their cars to the wind tunnel to gain that extra edge. Aero upgrades always have the same goals: downforce, front/rear balance and cooling at a minimal drag cost. In this article, we'll have a look at a selection of interesting cars in interesting tunnels around the world - and learn to say "Wind Tunnel" in different languagues!

## France - "Soufflerie"

Gustave Eiffel. Not only did he create the Eiffel tower, he had also designed a wind tunnel, located at the base of the tower. When he had to move it, he created the Laboratoire Aérodynamic Eiffel, featuring a wind tunnel which was used by Peugeot just 2 years after opening. Many years later, Peugeot took the 206 WRC and later the 307 WRC to the tunnel.

<ImageWithCaption
 src="/assets/images/rally-cars-307WRC.jpg"
 alt="Peugeot 307 WRC scaled model - Picture by Laboratoire Aérodynamic Eiffel"
 width="782"
 height="596"
/>

They used scaled models for both cars, which allowed them to test in smaller (and thus cheaper!) facilities. But scaling laws and velocity limits impose extra constraints on aerodynamic testing. So they also performed full scale testing at facilities such as the S4 wind tunnel of the Institut Aérotechnique (IAT), where they did the aerodynamic development of the 205 Turbo 16 in 1984.

The Laboratoire Aérodynamic Eiffel also served that other legendary French rally car manufactuer - Citroën. Some of the most successful rally cars like the Xsara WRC (2001), the C4 WRC (2006) and the DS3 WRC (2010) were tested here.

<ImageWithCaption
 src="/assets/images/rally-cars-DS3WRC.jpg"
 alt="Citroën DS3 WRC scaled model - Image credit: Zeppelin"
 width="819"
 height="546"
/>

Citroën also used the S2A (Souffleries Aéroacustiques Automobiles - jointly owned by PSA and Renault - see also our article on the Tesla Model Y that was tested there) for full-scale evaluation of the C4 WRC. Real conditions, real wind speeds and the lack of scale factors made this a very suitable tool to find extra aerodynamic performance.

## Italy - "Galleria del vento"

When you say "Rally" and "Italy", you say "Lancia Stratos". Most of the work, in terms of aerodynamics, was done in facilities close to Turin, Italy. The Lancia Stratos and the Lancia Rally 037 were both tested in the Pininfarina wind tunnel. This tunnel was opened in 1972 and was one of the first in the world to offer full scale testing for cars.

<ImageWithCaption
 src="/assets/images/rally-cars-lancia-stratos.jpg"
 alt="The Lancia Stratos prototype in the Pininfarina Wind Tunnel - Image credit: Lancia"
 width="1010"
 height="551"
/>

Back then (and still today), woollen tufts were one of the techniques often used to visualize the flow pattern on the surface of the car. These threads are so light that they are aligned with the local flow direction, providing the engineers with an opportunity to validate their assumptions (and simulations) made during the design phase.

<ImageWithCaption
 src="/assets/images/rally-cars-lancia-rally-037.jpg"
 alt="The Lancia 037 prototype in the Pininfarina Wind Tunnel - Image credit: Lancia"
 width="960"
 height="695"
/>

Also visible in some of these pictures are the load cells beneath the wheels to determine not only the total downforce but also the balance between front & rear downforce (the aero balance).

## Germany - "Windkanal"

Already back in 1966, Ferdinand Piëch (grandson of Porsche) believed strongly in the power of aerodynamics to win races when they were working on their LeMans race cars. The Porsche 906 won the Protos 2l category and finished 4t, 5th and 6th overall.

<ImageWithCaption
 src="/assets/images/porsche-911-carrera-rs-2.7.jpg"
 alt="Full-size Porsche Carrera 2.7 at the Stuttgart University Wind Tunnel - Image credit: Porsche"
 width="750"
 height="535"
/>

The famous ducktail was actually born in the wind tunnel as a means to reduce the lift problem they had by 50%. Also visible is the innovative way to measure the downforce at the front & rear independently by using a hanging support for each axis.

Piech was also known for being concerned with secrecy - the aerodynamic design work on the Audi 100 for example was spread over 5 different wind tunnels so that no one would see the full car. That definitely helps to explain why there aren't many pictures of German (or Japanese) cars in wind tunnels. We didn't find a single image of the Skoda Fabia WRC or the VW Polo WRC, both of which were tested in the wind tunnel.

## Japan - "風洞"

Mitsubishi honed the aerodynamics of multiple Lancer Evo Group A models in the wind tunnel of the Mitsubishi Heavy Industries Headquarters. Just like the famous Subaru Impreza WRC cars, which were tuned in the wind tunnel at the Fuji Heavy Industries HQ Because most rally activities were managed by European structures, some of the fine-tuning was done at European facilities, mostly in the UK.

<ImageWithCaption
 src="/assets/images/rally-cars-subaru-wrx-sti.jpg"
 alt="Subaru WRX STI in the wind tunnel - Image redit: Subaru Motorsport"
 width="796"
 height="524"
/>

One such example is the Mitsubishi Lancer Evo Group A: the baseline design was done at the wind tunnel in Japan but then Ralliart (a private rally team) used the S10 wind tunnel in France or the MIRA wind tunnel in the UK for further fine tuning. The latter was also host to cars like the Impreza WRC (Prodrive) the Ford RS200 and the MG Metro 6R4 (developed with the support of Williams F1).

## South Korea - "풍동"

Hyundai joined the WRC championship in 2014 and uses its in-house Hyundai Aero-Acoustic Wind Tunnel (HAWT) in Seoul. It can accommodate full-scale models and provides wind speeds up to 200 km/h.

<ImageWithCaption
 src="/assets/images/Hyundai-aero-acoustic-wind-tunnel.jpg"
 alt="Hyunday Aero-Acoustic Wind Tunnel Layout - Image credit: Hyundai"
 width="800"
 height="410"
/>

## Conclusion

Wind tunnels have played a key role throughout the development of many successful rally cars over the past decades and will continue to do so for a long time. They help designers & engineers to validate their assumptions / simulations so they can ultimately design a faster rally car.

More information:

<ExternalLink href="https://www.wrcwings.tech/2020/10/26/wind-tunnels-in-the-history-of-wrc/">
 The Full Article at WRC Wings
</ExternalLink>

[Video on Rally Car Aerodynamics](/videos/rally-car-aerodynamics-side-slipping-through-the-air/hGK2wRVcALs)

<ExternalLink
 href="https://app.airshaper.com/projects/new?accuracy=regular"
 target="_blank"
>
 Run your own Simulation
</ExternalLink>

Rally Cars in Wind Tunnels

## Introduction 📢

Werner Lodewijckx is CEO of <ExternalLink href="http://auto-access.eu/">AutoAccess</ExternalLink>, a company specialized in designing & manufacturing automotive accessories. One of their product lines are hard tops for pickup trucks. With the WLTP (Worldwide Harmonised Light Vehicle Test Procedure) emissions regulations increasing the pressure, aerodynamics have come into play to safeguard the fuel efficiency of the pickup.

## A Changing market

Pickups are having a tough time, especially when it comes to their emissions. The basic shape of a pickup truck is not the most rewarding one when it comes to aerodynamics, with a large frontal area, large open wheel spaces, a chopped-off cabin and an open cargo bay. The hard top covers we design & manufacture are there for functional purposes, like creating extra storage space for tools. But when adding a hard top cover to a pickup truck, one also impacts the aerodynamics. An increase in fuel consumption would be quite a negative aspect for both the customer and the regulators. Therefore, we went to work to make sure the latest cover we designed for the Isuzu D-Max wouldn't increase fuel consumption.

## Benchmarking

<ImageWithCaption
 src="/assets/images/pickup-truck-without-cover.jpg"
 alt="The aerodynamics of the Isuzu D-Max pickup truck without cove"
 width="1184"
 height="714"
/>

The first thing we wanted to do was to analyze the aerodynamic performance of the pickup truck without hard top cover. This would be our reference for any hard top we would design. As expected, we could see massive flow separation behind the cabin space and then again flow separation at the end of the cargo bay. Our hard tops fit exactly into that space, so we went to work with AirShaper to see how we could minimize the impact on the airflow or even improve it.

## Constraints

We first analyzed a conventional design, with a visual spoiler at the end of the hard top (to fit the central tail light) and a fairly boxy layout to maximize storage space & accessibility. The first results quickly showed that this kicked up the flow, increasing the size of the wake behind the vehicle and along with it the drag figure. In what followed, we iterated across different designs to balance cargo space, accessibility and a soft downward slope towards the end of the hard top. In a way it makes sense to simply provide the top with a downard curve, to obtain more of a drop shape, but in reality, there is a limit to this: overdo this and you'll see the drag figures go up again (let alone the loss in cargo space). So we kept tweaking it until we had found the optimum.

<ImageWithCaption
 src="/assets/images/cover-comparison.jpg"
 alt="Comparison between the conventional & new hard top design"
 width="1940"
 height="473"
/>

## The results

<ImageWithCaption
 src="/assets/images/isuzu-hard-top-cropped.jpg"
 alt="The final design of the aerodynamic Isuzu D-Max Hard Top"
 width="1334"
 height="671"
/>

We ended up with a design that lowered the aerodynamic drag by around 3% compared to a conventional hard top design. And what's even more impressive, it even slightly lowers the drag compared to a pickup truck without a hard top cover. We're quite happy that despite all this we were able to maintain our typical visual style for the hard top.

Interesting links:

<ExternalLink href="http://auto-access.eu/">AutoAccess</ExternalLink>
 

[Running your own simulation](/videos/how-to-run-an-aerodynamic-simulation/O_DNDxCtI_I)

[Tesla Semi Aerodynamics](/videos/truck-aerodynamics-tesla-semi-explained/Km1NHe0ZsVo)

Pickup Truck Aerodynamics

## Introduction 📢

Train aerodynamics is a fascinating, yet sometimes forgotten world, particularly with the increasing number of high-speed trains that are currently in use worldwide. We had the pleasure to interview two experts working at <ExternalLink href="https://www.caf.net" >CAF</ExternalLink>, a rail systems company born in the Basque Country (Spain) which designs, manufactures and maintains rail systems around the globe. Joseba Murua, head of the dynamics and rolling area within the R&D department, leads a team focused on analysing suspension forces and vehicle–track interaction. On the other hand, Mikel Iraeta works in the fluids mechanics department, predicting the external aerodynamic phenomena related to high-speed trains.

<ImageWithCaption
 src="/assets/images/CAF-oaris.jpg"
 alt="The CAF Oaris train - Image credit: CAF"
 width="800"
 height="542"
/>

## The role of train aerodynamics

**What are the main focus points when working on the aerodynamics of trains?**

(Mikel) Acknowledging that trains are a means of transport used daily by millions of people, passenger safety is a top priority. My team ensures that European guidelines are followed, such as the Council Directives on interoperability of the trans-European high-speed and conventional rail systems and the Technical Specifications for Interoperability (TSIs). Safety is determined by the stability of the train as well as its functioning in case of failure or accident.
Although train aerodynamics varies greatly among the different types of vehicle to be analysed and is highly dependent on operating conditions such as speed range, exposure to crosswinds, altitude and tunnel operation, there is a common focus point: efficiency. There is an increasing demand from the European Union towards designing long-term sustainable vehicles which maximise energetical performance. This implies an improved vehicle design based on experience, collected data and simulations (predicting drag, head pressure waves and crosswind stability, among others) that shall lead to a better train performance and tends to avoid the overestimations of components.
(Joseba) The increased efficiency requirements have a crucial impact on the vehicle system dynamics, which we analyse by evaluating stability behaviour, curve negotiation, rolling physics and train-infrastructure interaction, among others. In particular, the response to cross winds has to be considered.

<ImageWithCaption
 src="/assets/images/train-aerodynamics-cfd-mesh.jpg"
 alt="Computational mesh for the CAF Civity train - Image credit: CAF"
 width="1980"
 height="1080"
/>

## Crosswind Effect

**What is the importance of crosswind and how does it affect train dynamics and safety?**

(Mikel) The stability against crosswind is a technical compatibility problem that can be described by three aspects:

- The wind speed a vehicle is able to withstand in some reference conditions
- The wind exposure of the line
- The characteristics of the infrastructure

This means that equivalent wind conditions (in terms of wind speed and angle of attack) will not necessarily have the same effect on all trains. For example, the resulting wind force acting on a vehicle running over a 6 m high embankment will be different from the resulting force acting on a vehicle running on a flat ground for the same wind conditions.
The role of the train manufacturers is to determine the wind speed the most sensitive car of the unit is able to withstand for some given conditions. At European level this is carried out according to the EN14067-6:2018 which is the normative reference for this purpose and is applicable for vehicles running above 140 km/h. The methodology described in the standard implies:

- An aerodynamic characterisation of the studied vehicle. This is normally carried out by wind tunnel tests where the aerodynamic coefficients are obtained.
- A characterisation of the vehicle performance against crosswinds. For this purpose multibody simulations are usually performed by using a validated vehicle model that uses some input data such as the previously obtained aerodynamic coefficients

As a consequence of this process a number of CWCs (Characteristic Wind Curves) are obtained, which show the wind speed the vehicle is able to withstand for certain simulated conditions.
However, establishing a safe operation strategy is the responsibility of the infrastructure manager, who is given inputs on train assessment, infrastructure characteristics and path environmental characteristics.
The higher the train speed, the more sensitive it is to perturbations and the more likely (although worst case scenario) overturn is.

(Joseba) We must therefore estimate the dynamic response of trains after a velocity perturbation or lateral force, as in aircraft aerodynamics.

## Head pressure pulse & slipstream

**The effect of a train passing through a station is also an important aspect. Can you detail how this affects safety of passengers and railway workers?**

(Mikel) In order to answer this question, we must first picture a train as a large mass in movement that disturbs the pressure and velocity field around it. The acceptable amount of perturbation is determined, once again, by the TSI and the European Standards (EN) that determine the limit of acceptable pressure variation and wind speeds.
The safety distance (measured relatively from the person to the closest surface of the vehicle) is determined by the magnitude of the velocity and pressure induced, which is directly proportional to the size and geometry of the train.
Although a more appropriate approach to this question is "what is the velocity at which the train should be approaching", rather than "what is the safe distance at which passengers should be from the train". It is for this reason that the train velocity is always reduced when approaching a station.

<ImageWithCaption
 src="/assets/images/train-aerodynamics-pressure-slice.jpg"
 alt="Static pressure at the front of the CAF Oaris train - Image credit: CAF"
 width="1920"
 height="956"
/>

## Tunnel train performance

**What are the main challenges associated with tunnel entrance and exit?**

(Mikel) As mentioned, when a train is in movement, it displaces a large air volume around it. When the vehicle is in open air, this perturbation is not constrained, unlike in tunnels, where air displacement is limited by the tunnel’s cross section.
At the entrance of the tunnel, part of the air perturbed is displaced forwards as a wave front while part of the air is moved rearwards out of the tunnel..
Every time a train enters or leaves a tunnel it creates a pressure change that will be higher or lower than the given atmospheric pressure. This pressure variation is propagated into the tunnel as a wave front at the speed of sound. When the pressure wave reaches the end of the tunnel, it is partly dissipated into the atmosphere while the rest is reflected back at the portal. In case the incident wave front was above the atmospheric pressure (which is the case when the train head enters the tunnel) the reflected wave at the opposite portal will be under the atmospheric pressure and vice versa.
When the tail of the train enters the tunnel, a similar process occurs: the wave front below the atmospheric pressure travels upstream and will be reflected at the opposite portal as a wave front above the atmospheric pressure.

All of these waves cause two phenomena to occur simultaneously. On the one hand, in the vicinity of the train surface, a quasi static flow field can be assumed (even if it is not strictly quasi static, the observed variations may be considered negligible to the overall values). On the other hand, the train will be moving through a complex superposition of waves due to the interaction with the wave fronts. Additonally, the air between the tunnel walls and the train surface will be constrained, as the combination of wall and surface boundary layer growth reduces the effective area in between. The smaller the ratio of tunnel to train cross section, the more significant this effect will be which can have a big impact on the wave fronts and the drag in tunnel.

**Does the interaction between these compressible waves cause vibrations in the train?**

(Mikel) A vibration may be induced and noticed by passengers at the entrance and exit of the tunnel, but not along the journey inside the tunnel. A small impulse is induced, but is not constant nor periodic, as the impulse is quickly normalised.

**How can the “tunnel boom” occur even if trains rarely travel above Mach 1?**

(Mikel) When the front wave reaches the end of the tunnel, the energy transmitted to the outside is propagated in a way that can produce a sonic boom. After all, we are talking about a large variation in pressure within a very short timescale and this can be manifested in an audible manner known as tunnel boom.
This potential boom would not be perceived by the passengers, as the pressure waves are propagating much faster than train speed. It would only be heard by someone standing outside the tunnel, which is why special consideration must be given to this effect if people live in the vicinity of a high-speed train tunnel. Moreover, it’s a complex phenomenon, difficult to predict as it doesn’t occur in all trains nor tunnels, only within specific characteristics and speed ranges.

**Is the induced pressure on the windows significant enough to be considered?**

(Mikel) The pressure inside the tunnel is limited by regulations to ensure that windows do not burst under pressure.
(Joseba) Both the pressure and velocity inside tunnels are estimated using our own application, which was developed between CAF and the Universidad Politécnica de Madrid. A full CFD analysis is not required in this case and therefore a computationally less costly application can be used.
(Mikel) The pressure experienced by the surfaces is determined so that manufacturers can design the windows and doors accordingly.
Although window burst due to pressure is not very worrying, special attention must be taken when considering the scenario of debris impact that has a higher probability of bursting a window. This would induce a great pressure variation that could be harmful to passengers, causing ear damage. Once again, the maximum pressure variation acceptable is set by safety standards.

## The pantograph

**What is the effect of the pantograph on the aerodynamics of the train?**

(Mikel) Pantograph effect is only considerable at high speeds, where it can cause not only aero acoustic issues, but also propagate waves in the catenary. Moreover, it is important to understand that the pantograph is a contact between a metallic thread and a rubbing band. It is this contact that provides the energy supply to the train and therefore, it should not be interrupted. The contact must be constant and stable, which is difficulted in the presence of oscillatory forces that may indeed be aerodynamic forces but can also be induced by mechanical movements. To ensure stability, dynamic tests are performed to estimate the forces experienced and the number of actuators and dampers required. It is very difficult to simulate, which is why it is mostly based on experimental data.

(Joseba) The aerodynamic effect of the pantograph is quite peculiar, because although it is very local (as it only acts within a small percentage of the train’s surface), it is highly affected by the globality of the train. The boundary layer developed upstream of the pantograph is critical and complex to predict, and the velocity profile seen by the pantograph is very intricate and three-dimensional, particularly acknowledging the disturbances that roof-mounted systems cause on the flow field.

## Frontal Shape Efficiency

**How is the train’s head designed to ensure maximum efficiency?**

(Mikel) There isn’t a direct answer, as we need to consider for which parameter is the head optimised for, depending on the vehicle to be designed. It is evident that in trams and subways, the frontal shape is not very important, but as operating velocity increases, the head will have different functions and will affect factors like the wave front and pressure waves strength, stability, drag and crosswind effects, as the geometry can condition the way flow is propagated downstream and its interaction with other train systems.
Therefore, an “optimal” design cannot be found such that it minimises all detrimental effects, but a good enough design can be found such that it satisfies all requirements.
Usually, past vehicle data is used as reference on which innovative designs are based, which are later validated in railway trials or wind tunnel tests.

<ImageWithCaption
 src="/assets/images/train-aerodynamics-pressure-contours.jpg"
 alt="Static pressure countours around the CAF Civity - Image credit: CAF"
 width="3840"
 height="2160"
/>

I am particularly fascinated by Japanese trains heads, whose lengths can range up to 15 m, far larger than the maximum 6 m commonly designed in Europe.
One would be surprised with such design, particularly because the nose cannot host passengers and it is therefore “unused” space which could theoretically minimise the financial benefits of such train. But it is because of the bullet trains operating speeds of over 300 km/h that these noses are needed to avoid tunnel booms. They ensure that the transition of free area to tunnel restriction is more gradual, such that the pressure waves act within a longer timescale, progressive, alleviating this phenomenon and attenuating the sonic boom effect.

## An aeronautics point of view

(Joseba) Having an aeronautics background, it is interesting to present an analogy and a difference between aircraft aerodynamics and train aerodynamics.
Starting from the analogy, in both cases their design is highly limited and determined by safety considerations. At the end of the day, it is human lives that are at risk on both vehicles. It is for this reason that all developments and changes undergo a great quantity of checks and standard compliance before they can be introduced in the market. All aerodynamic analysis and predictions must have solid foundation that can back up the safety of their implementation.
With regards to the main difference, an airplane is a lifting body while a train is not, which is why much of the aerodynamic knowledge that was obtained a century ago is not always applicable to the analysis of trains.
I particularly believe that the aerodynamical theoretical foundation of trains has not been as widely studied and developed as airplane aerodynamics, which is why we must, more often than not, rely on simulations and empirical data to obtain the knowledge that we require of our vehicle.

Interesting links:

<ExternalLink href="https://www.caf.net/">CAF</ExternalLink>
 

<ExternalLink href="https://app.airshaper.com/projects/new?accuracy=regular">
 Run Your Own Simulation
</ExternalLink>

High-speed Train Aerodynamics

## Introduction 📢

For this blog post, Nicolas Berberoff interviewed James Warren, head of communnication at <ExternalLink href="https://www.airspeeder.com">Airspeeder</ExternalLink>. Airspeeder is an upcoming racing series with a bespoke Octocopter set to reach speeds of up to 200 km/h!

## Racing to solve congestion?

<ImageWithCaption
 src="/assets/images/speeder1.jpeg"
 alt="The high-performance AirSpeeder Octocopter"
 width="1080"
 height="720"
/>

**Talk us through the actual nature of this competition, the origins of the company. Why translate motorsports to the aerospace sector?**
One must start by apprising the scale and potential of electric takeoff and landing (eVTOL) vehicles, the next great mobility revolution. In its commercialised form it promises to liberate our cities from congestion, massively cut journey time in urban areas and revolutionise aerial logistics. This industry is estimate to be worth more than 1.2 trillion dollars by 2040, backed by the likes of Uber, Daimler, Toyota, Porsche and many other manufacturers.
What we have envisioned is that despite the shift to autonomous transport, there will always be a desire amongst people to drive or pilot vehicles. Our founder Matt Pearson, after finding success in a technology start-up in south Australia, found himself in a position where he had time and resources on his hands and was frustrated he couldn’t buy a flying electric car, something we have been promised for years in science fiction.
He decided to investigate the automotive history and aviation to see what elements accelerate the development of such technologies, assessing how mobility revolutions have come across and societal acceptance has been built up. Competition is within human nature; thus, racing will always remain relevant. Historically competition has propelled the acceptance and incorporation of such technologies into our lives, so we at Airspeeder are playing that same role with the revolution of flying cars.

**Establishing a bond with society is important, technology must be relevant. How does Airspeeder intend to impact society?**

We impact society in the sense that we are working towards a technology that will liberate congestion, by utilising a clean-air technology, let’s not forget the environmental impact too. We are proud of the role we are already playing in hastening that technology; bringing to maturity quicker, answering safety questions quicker, being more robust in testing or even addressing noise pollution quicker than the design process of a passenger craft will.
Hence the technological advances that we are making, are going to make the development of passenger taxies possible, underpinning the technology that will eventually be there. Racing but with purpose, much in the line of what Formula 1 has brought us; ABS, energy recovery systems etc.

## A Blank Sheet of Paper

<ImageWithCaption
 src="/assets/images/speeder2.jpg"
 alt="The Airspeeder - Literally taking the race from the tarmac to the sky"
 width="1920"
 height="1080"
/>

**Will this be considered motorsports? How are other racing institutions reacting to this?**

We are widely regarded, certainly in racing communities, as the Formula 1 of the skies. There are several implications to this. Number one, when you are defining a new sport, new technology and craft to go with it, you start with a completely blank sheet of paper. We are not having to fight against the traditions or legacies that other sports might face. Thus, we can design the sport from a conceptual stage, defining its essence, deciding the way that we enable teams to approach racing.
For example, we as Alauda Aeronautics Pty Ltd. will supply the craft to different teams so that the technological plane field will be completely even. Hence allowing teams to have separate strategies and recruit their own pilots, resulting in an ‘ideal’ equitable competition that we, all motorsports fans, want to see. Without doubt, it will certainly be something people will globally respond to. In terms of how we interact with our fans, we are yet exploring; not bound to existing broadcast agreements or restricted in any other way, we have complete freedom. The way we are approaching the spectator interaction is as a very two-way competition; fans will be able to live-stream the races, interact with the pilots and engage with the sport itself.

**Currently there are openings for pilots. What backgrounds or requirements should those pilots have?**

Again, starting form this blank sheet of paper, we made an open call to elite pilots. Back in June, Matt Pearson spoke in an event hosted by an organisation called Mobility Prime; basically, the US AirForces’ accelerator eVTOL technology. People have come to us from a range of backgrounds; test pilots from civil and military backgrounds, very strong acrobatic and competition pilots. To our minds, we don’t want to limit it, we are making an encouraging call to strong UAV or even drone pilots. Same thing goes with people from esports.

**With there be different locations across the season?**
Number one focus at the moment is in 2021. We have already spoken about Coober Pedy desert in South Australia, or the Mojave Desert. During this first season (season alfa), there will likely be one-on-one time trial races or duels. In the future it will be opened up for a much larger grid. Note that our MK4 craft, reaches 130kph, flying around an electronically governed circuit around the locations in time trial. Eventually everything will build up to more traditional close-racing events. Technology is ready; by combining lidar sensors and virtual force fields we will liberate our pilots to race each other hard.

## High Tech Racing Nostalgia

<ImageWithCaption
 src="/assets/images/speeder3.jpeg"
 alt="The Airspeeder blends nostalgic design cues with high-tech performance"
 width="1080"
 height="719"
/>

**Design seems to be inspired by Formula One cars from the fifties with the air intake at the front, I suppose this also satisfies cooling requirements for batteries and systems? How much performance are you getting from batteries, range-wise, maximum thrust and so on?**

Our Head of Design, Felix Pierron really worked to create a profile that instantly evokes the sense of a racing craft. This is so important to building enthusiasm and acceptance for Vertical craft like ours. In many ways, design of a flying racing car is dictating by the need for performance in the same way the F1 cars of the fifties and beyond were. Air intakes are therefore not superfluous they are there to cool the high performance electric powertrain. While our contemporaries in the eVTOL passenger sector are focused primarily on range, efficiency and the ability to carry large loads we can be very focussed in developing the vehicle for pure performance and manoeuvrability. We will race at speeds of up to in 20 minute bursts with rapid pitstops that will really add to the drama and tension on race-days. We aim to race at speeds up to 200km/h.

<YouTubeEmbed
 videoId="Fl0hl2_E9Mg"
 title="How eVTOL Flying Cars Are Made | Airspeeder Factory Tour at Goodwood SpeedWeek"
/>

## Blending Design, Safety and Aerodynamics

<ImageWithCaption
 src="/assets/images/speeder4.jpeg"
 alt="The Airspeeder will even feature pitstops!"
 width="1000"
 height="1000"
/>

**How did you work on aerodynamics in general: lots of simulations? Did you involve industry experts? Did you / do you plan on doing wind tunnel tests?**

We’ve gathered a team of engineers and designers drawn from both the aviation and performance automotive worlds. With that, we are able to blend knowledge and processes from multiple disciplines including computer modelling and simulation. They will work with wind tunnel testing to hone aerodynamics that are then validated through extensive flight testing.

**Why this layout (4 double props on each corner)? Very good for manoeuvrability, less energy-efficient?**
The real benefit of the a performance eVTOL craft in this configuration is the rapid manoeuvrability that physics dictates is not possible with more traditionally specified aircraft. In essence, our pilots will have the same rapid hairpin turning ability at their disposal as an F1 driver but with the addition of a third dimension because we’re in the air. We refer to our layout as an octocopter ‘H configuration’ - this adds an important layer of safety as it adds redundancy. In event of a motor failure the craft will not become unstable as per a traditional quadcopter setup.

**The "rotor arms" have been given an aerodynamic profile, is that correct? How do they contribute to the performance of the aircraft?**
Like any craft participating in an elite sport, every surface or function must be honed to do perform optimally. Our philosophy here is that form must absolute service function, therefore the shape of the rotor arms does much to make the craft move through the air efficiently which provides enormous benefits in terms of overall performance and manoeuvrability. To go into more detail, they have an airfoil profile to improve performance by generating lift and reducing drag.

<YouTubeEmbed
 videoId="JaAVelVsaU4"
 title="Powering Up Our eVTOL Flying Car | Airspeeder"
/>

## Conclusions

The Airspeeder series promises to pave the way for new urban air mobility technology as well as to entertain the masses. Will the virtual force field hold under the pressure of racing? Will the pitstops cause drama during the races? And most importantly, does air mobility really hold the key to sustainable transportation, truly reducing CO2/km without shifting the congestion problem to the skies? Let's find out when the Airspeeder series kicks off in 2021!

Interesting links:

<ExternalLink href="https://www.airspeeder.com">Airspeeder</ExternalLink>
 

<ExternalLink href="/videos/nascar-in-the-sky-interview-with-air-race-e/kcx23YY1Kms">
 Air Race E
</ExternalLink>
 

<ExternalLink href="/blog/formula-air-grand-prix">
 Formula Air Grand Prix
</ExternalLink>

AirShaper BlogPassion for aerodynamics

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The Case of the Mercedes EQC Drag Coefficient

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Camera Pod Aerodynamics

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Rally Cars in Wind Tunnels

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Pickup Truck Aerodynamics

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High-speed Train Aerodynamics

Claudia Jiménez Cuesta

Airspeeder - The Electric Flying Car Racing Series

Nicolas Berberoff Naval

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