## 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/video/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"
 layout="responsive"
 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 sown)"
 layout="responsive"
 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 sown)"
 layout="responsive"
 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/video/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"
 layout="responsive"
 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"
 layout="responsive"
 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/video/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"
 layout="responsive"
 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"
 layout="responsive"
 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"
 layout="responsive"
 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"
 layout="responsive"
 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"
 layout="responsive"
 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"
 layout="responsive"
 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"
 layout="responsive"
 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/video/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"
 layout="responsive"
 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"
 layout="responsive"
 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"
 layout="responsive"
 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/video/O_DNDxCtI_I)

[Tesla Semi Aerodynamics](/videos/truck-aerodynamics-tesla-semi-explained/video/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"
 layout="responsive"
 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"
 layout="responsive"
 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"
 layout="responsive"
 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"
 layout="responsive"
 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"
 layout="responsive"
 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"
 layout="responsive"
 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"
 layout="responsive"
 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!"
 layout="responsive"
 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/video/kcx23YY1Kms">
 Air Race E
</ExternalLink>
 

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

Airspeeder - The Electric Flying Car Racing Series

## About the Author 📢

Sheetalkumar Patil is founder and director of <ExternalLink href="/partners/engineering/speed-engineering-solutions">Speed Engineering</ExternalLink> where they focus on engineering for a wide variety of segments like aerospace, automotive, electronics and so on. In this article though, the speed is much reduced as he takes us through the process of optimizing the aerodynamics of the famous Rickshaw at just 15 m/s.

## Introduction

When people think of aerodynamics, they automatically think of airplanes flying at 800 km/h, rockets blasting into space or race cars lapping the Nürbürgring at insane speeds. But aerodynamics play a role as any object starts to move through the air, no matter how low the speed. And they start to play a significant role, i.e. an impact on fuel consumption & range well above 10%, at much lower speeds than people would expect. In this article, we dive into the details of the Rickshaw, one of the most popular vehicles in India & Sout-East Asia. And we come to the conclusion that much can be gained from improving its aerodynamics!

## Bluff body aerodynamics

In fluid mechanics terms, vehicles are bluff bodies travelling very close the ground. A complex three-dimensional flow occurs around the vehicles with flow separation being very common. Such flow is typically analysed and optimized through external aerodynamics studies.

Sports cars, passenger cars and commercial vehicles - all of which move at relatively high speeds - experience significant aerodynamic drag forces which impact performance and increase fuel consumption. For ground vehicles, this is mainly pressure drag; so avoiding or reducing the separation is one of the main objectives of vehicle aerodynamics.

External aerodynamics is also becoming increasingly important in the shift from fossil fuel vehicles to electric vehicles. In the context of electrification of vehicles, the drag force is an important factor to be considered as it impacts the operating costs of the vehicles, sizing of the drive train and the range of the vehicle before recharge. Reducing drag force is important even for relatively slower speed electric vehicles and if not optimized, it can have significant impact on cost and performance. Therefore, design improvements through external aerodynamics simulations of drag resistance using CFD is a necessity for all electric vehicles.

External aerodynamics simulations using CFD though have some constraints, such as:

- Huge time required to create watertight geometry. This task is very tedious.
- High-end hardware requirement to reduce the analysis turnaround time (high RAM and number of CPU cores etc.).
- Huge computational costs. Major drawback of high-end computation is cost (hardware + software license).
 During the conceptual and preliminary design phases, these constraints may prove detrimental to the project's timeline and budget.

Here we are presenting a case study to depict how CFD analysis can be used to improve aerodynamics of a relatively slower speed commercial vehicle while overcoming the above constraints.

## The Baseline Rickshaw Design

This case study has been performed on the legacy design of auto rickshaw (3-wheeler). It is mainly used as short distance taxi in India and South Asia. The body design was done in the last century and aerodynamic considerations were not the primary factors back then. If we want to convert such vehicle to an electric one, we need to consider aerodynamics and check how much electric power can be saved and also, if the range can be increased through design improvements to the body shape.

The shape of the 3-wheeler considered for this study is as shown below.

<ImageWithCaption
 src="/assets/images/3wheeler_baseline_design.jpg"
 alt="The baseline Rickshaw 3-wheeler design"
 layout="responsive"
 width="1182"
 height="776"
/>

- This design is primarily used with a gasoline engine.
- Engine power rating is around 7.5 kW@4500 RPM with a peak torque of 19 Nm@3200 RPM
- Carries a maximum of 4 people - 1 driver + 3 passengers.
- The range of the vehicle is around 350km with full tank.

## Revised Design

Based on the AirShaper results of the external aerodynamics study on the baseline design, the body shape was revised within the following constraints:

- Change in overall envelope should be minimal. No change in the ground clearance.
- No change in the drive-train interfaces (track, wheelbase etc.)
- Driver and passenger comfort should not be affected. No interiors should be affected.
- No major changes in ergonomics etc.

The following changes were made to the baseline design:

- The underfloor was made flat. All the steps are removed.
- The roof was given a downward slope towards the rear to delay separation.
- The frontal area was made more round.
- A feature just above the rear wheels was added to bleed air in the wake region.

The revised design is depicted below.

<ImageWithCaption
 src="/assets/images/3wheeler_revised_design.jpg"
 alt="The revised Rickshaw 3-wheeler design"
 layout="responsive"
 width="1327"
 height="829"
/>

## Simulation Results

Both designs were analysed for aerodynamic performance at a vehicle speed of 15 m/s. The drag coefficient of the Rickshaw has dropped form 0.45 to 0.39. This reduces the power required to overcome aerodynamic forces by 17.4 %. This will result in an increase in the range of the vehicle as well.

<ImageWithCaption
 src="/assets/images/3wheeler_drag_curve.jpg"
 alt="The drag coefficient of the baseline and revised Rickshaw design"
 layout="responsive"
 width="1287"
 height="367"
/>

<ImageWithCaption
 src="/assets/images/3wheeler_drag_table.jpg"
 alt="The drag force & power of the baseline and revised Rickshaw design"
 layout="responsive"
 width="663"
 height="302"
/>

The aerodynamic plots below, comparing the baseline & revised design, show how various aerodynamic considerations were implemented:

- The wake should be as small as possible (see "red clouds" behind the vehicle). This was achieved by an improved roof line, the removal of steps in the underfloor and the bleeding of air into the wake via slots on the sides of the vehicle.
- The pressure build-up at the front was reduced by increasing the radius of the front of the vehicle.
- The number & size of separation locations was reduced by eliminating steps at the underfloor, sharp edges at the front, and so on.
 The modifications done on the baseline geometry based on the recommendations by CFD analysis show significant improvement in the drag performance of the vehicle.

<ImageWithCaption
 src="/assets/images/3wheeler_pressure_clouds.jpg"
 alt="The aerodynamic wake locations of the baseline and revised Rickshaw design"
 layout="responsive"
 width="1289"
 height="511"
/>

<ImageWithCaption
 src="/assets/images/3wheeler_surface_pressure.jpg"
 alt="The aerodynamic surface pressure locations of the baseline and revised Rickshaw design"
 layout="responsive"
 width="1315"
 height="602"
/>

<ImageWithCaption
 src="/assets/images/3wheeler_streamlines_side.jpg"
 alt="The 3D streamlines around the baseline and revised Rickshaw design - side view"
 layout="responsive"
 width="847"
 height="733"
/>

<ImageWithCaption
 src="/assets/images/3wheeler_streamlines_top.jpg"
 alt="The 3D streamlines around the baseline and revised Rickshaw design - top view"
 layout="responsive"
 width="933"
 height="719"
/>

## Efficiency

The total project was done in just 50 hours, of which 40% was CFD run time. The rest of the time was spent on geometry modifications, post-processing the data and drawing conclusions & reporting. So, computationally this is not a very expensive analysis.

## Conclusions

- Estimating the performance parameters related to external aerodynamics by CFD during vehicle development can yield significant benefits even for relatively slow vehicles.
- Design improvements to the body shape based on external aerodynamics can help reduce drag, reduce power consumption and improve range. This is especially important for electric vehicles.
- The CFD analysis method presented here, gives an opportunity to perform external aerodynamics CFD analysis at very low cost and which is adequately accurate. In this arrangement, multiple CFD analysis iterations of external shapes are possible within a short timeframe.

Interesting links:

<ExternalLink href="/partners/engineering/speed-engineering-solutions">
 Speed Engineering
</ExternalLink>
 

<ExternalLink href="https://app.airshaper.com">
 Running your own CFD Simulation
</ExternalLink>
 

<ExternalLink href="/videos/cfd-results-how-to-interpret-an-aerodynamic-analysis/video/XntO27S5Urc">
 How to interpret a CFD Simulation
</ExternalLink>

Rickshaw Aerodynamics - Drag at 15 m/s

## About the Author 📢

Yann Le Fraillec works at <ExternalLink href="https://www.decathlon.com">Decathlon</ExternalLink> as Project Manager, engineering bikes, helmets and more. In this article, he explains how they benchmarked the aerodynamic of their own helmets versus that of the competition. To that end, they used 3D scanned models made by <ExternalLink href="/partners/engineering/jf3d">JF3D</ExternalLink> and ran those through AirShaper for a digital comparison.

## A New Identity

Up until 2019, all Decathlon bikes & helmets were part of the BTWIN label. But as of January 2019, Decathlon decided to use the BTWIN brand mainly for kids bikes and create 2 additional brands for the road bikes, each with a different identity:

- Triban: aimed at enjoying cycling in a comfortable way
- Van/Rysel: aimed at performance, with less compromise towards comfort. Named after the Flemish name of Lille, the city where Decathlon HQ & BTWIN Village are located. And perhaps more importantly, Rijsel (Lille) is the capital of the (French) Flanders region - the cycling-walhalla with classics like Paris-Roubaix!

## Van/Rysel - On a mission

There are numerous challenges to developing a performance brand: each product needs to improve on the performance & experience of the rider. When we dediced to create an aerodynamic helmet, we needed a starting point. We applied digital simulations to our own helmet to understand the airflow. In a first iteration, we compared our new design to our existing Endurance helmet, the Van/Rysel 900.

<ImageWithCaption
 src="/assets/images/aerodynamic_comparison_decathlon_old_new_helmet.jpg"
 alt="Aerodynamic comparison between the existing Van/Rysel helmet and the new design"
 layout="responsive"
 width="1916"
 height="452"
/>

The simulations provided us with good insights, but the real challenge came when comparing to the competition - that was an entirely new game.

## Benchmarking the competition

We had 3D scanned models of Ekoi and Giro helmets and mounted those on a "generic" head to have an objective reference.

<ImageWithCaption
 src="/assets/images/3d_scans_of_helmets.jpg"
 alt="3D scans of the Van/Rysel Giro & Ekoi helmets position on a generic dummy head"
 layout="responsive"
 width="2000"
 height="751"
/>

Of course much depends on the "angle" of this head (tilting a bit more forward or backward can really change the ranking), but we had to start somewhere. When the results of our first design came in, they were bad and simply not acceptable for a performance brand claiming to deliver performance.

<ImageWithCaption
 src="/assets/images/aerodynamic_drag_cycling_helmets.jpg"
 alt="Aerodynamic comparison between the Van/Rysel, Giro and Ekoi helmet"
 layout="responsive"
 width="1999"
 height="539"
/>

## Aiming for the win

So we kicked off an aerodynamic development track together with AirShaper to improve the performance of our design. Digital simulations provide an easy and flexible way to virtually test the aerodynamics and learn as you go at a reasonable cost. And scanning competitor helmets to benchmark our own design is a really powerful and efficient way of making progress. Using the results, our design & engineering team is working hard to deliver drastic aerodynamic improvements. Our goal is to provide one of the most aerodynamic helmets out there and we won't stop until we achieve that.

Interesting links:

<ExternalLink href="https://www.decathlon.com">Decathlon</ExternalLink>
 

<ExternalLink href="/partners/engineering/jf3d">JF3D</ExternalLink>
 

<ExternalLink href="https://airshaper.com/videos/sports-aerodynamics-1-winning-the-ironman-triathlon/video/DqlDpUFcScc">
 From 3D scan to Aerodynamic Analysis
</ExternalLink>

Decathlon explains - Using 3D scanning & simulations to design aerodynamic helmets

## About the Author 📢

Vincent Keromnes works at <ExternalLink href="/partners/engineering/a2mac1">A2MAC1</ExternalLink>, a company specialized in benchmarking the performance of cars. Lots of cars. Vincent is in charge of what they call "Dynamic Benchmarking", covering Kinematic & Compliance testing, Energy Management Strategy, Battery Thermal management and so on. With his hands on full 3D models on nearly every major car out there, he couldn't resist tweaking one of those cars on AirShaper to improve the aerodynamics :)

## Introduction

The launch of a new generation of the VW Golf is always seen as a major automotive event. A few months ago, we had already ran an AirShaper simulation on the Golf V (one with doors closed and <ExternalLink href="https://www.linkedin.com/pulse/my-first-aero-encounter-pushing-door-open-180-kmh-golf-remmerie-">one with Wouter's foot pushing the driver door open</ExternalLink> 😉) and on the Alltrack version of the Golf VII. So with the arrival of the Golf VIII at A2MAC1, we were curious to see the evolution in aerodynamics over the years. Also, we couldn't stop wondering if there might be ways to further improve fuel consumption with minor tweaks to the car.

## From Golf V to Golf VIII

### Roofline

As you can see on the profile picture with the "pressure clouds" (isosurface for Cp equal to zero), the aerodynamicists have had lots of influence on the shape of the car, in particular with the end of the roof that is now really going down with a bigger spoiler thus reducing efficiently the height of the wake. You can also notice the A pillar improvement including the side view mirror area.

<ImageWithCaption
 src="/assets/images/golf_8_total_pressure_cloud_comparison_side.jpg"
 alt="Drag analysis of Golf V versus Golf 8 - Side view"
 layout="responsive"
 width="1765"
 height="1109"
/>

### Wheels

The wheels of the VIII are far bigger and larger than on the V. This results in a larger wake close to the ground. But as you can see on the front picture this is balanced by an improved frontal coverage of the tire by the front bumper. As a consequence, the global efficiency of the wheel arch area is improved.

_Note: a reader has pointed out that there was no change to the available choice of tyre widths and sizes from Golf 5 to Golf 8_

<ImageWithCaption
 src="/assets/images/golf_8_total_pressure_cloud_comparison_front.jpg"
 alt="Drag analysis of Golf V versus Golf 8 - Front view"
 layout="responsive"
 width="1379"
 height="1205"
/>

### Underbody

It's interesting to see that the famous golf ball structure was applied to the aero shield of the V version but abandoned on the VIII (it was already gone on the VII). At the same time, Audi has been making a lot of marketing around the use of this pattern on the underbody of the etron …

<ImageWithCaption
 src="/assets/images/golf_5_golf_ball_dimple.jpg"
 alt="Golf ball dimple pattern on the underfloor of the Golf V"
 layout="responsive"
 width="2046"
 height="963"
/>

Apart from that side fact, it's quite remarkable that on the Golf VIII, as you can see on the picture, it looks like the underbody coverage extends backward only up until underneath the rear doors.

<ImageWithCaption
 src="/assets/images/golf_8_underfloor_dimension.jpg"
 alt="The underfloor cover of the Golf VIII doesn't extend all the way to the back"
 layout="responsive"
 width="784"
 height="441"
/>

We could argue that it’s a challenging (and expensive) job to cover the areas with high levels of heat dissipation (exhaust line and associated products) but if we look at the underbody of the eGolfVII we can still see that the underfloor coverage stops before the battery pack.

<ImageWithCaption
 src="/assets/images/e_golf_8_underfloor_dimension.jpg"
 alt="The underfloor cover of the e-Golf extends further, but also not all the way to the back"
 layout="responsive"
 width="784"
 height="441"
/>

### The numbers

The drag coefficient Cd has been improved by more than 12% from Golf V to Golf VIII. It’s important to notice that at the same time the frontal area has remained the same (about 2.23 sqm). That means that **from Golf V to VIII the overall drag has dropped by more than 12%**.

## Improving the Golf VIII Aerodynamics

### Design

Perhaps the underfloor wasn't extended all the way to the back because the gains in efficiency were too small? We kept wondering how much such efficiency gain would be, so we decided to design our very own "aero shield" by applying a few geometry modification. It is nicely cut (well, we did our best :) ) to respect the constraints of the hot parts from the exhaust line. As a consequence, it’s still not perfectly flat but it may be able to contribute to some improvement.

<ImageWithCaption
 src="/assets/images/golf_8_aero_shield_design.jpg"
 alt="The A2MAC1 aero shield design for the Golf VIII"
 layout="responsive"
 width="784"
 height="472"
/>

### Aerodynamic Simulation

Proud of our design, we then launched simulations of the Golf VIII without and with aero shield to see how it would perform. Below you can see the effect it has on the flow underneath the car. The aero shield helps to maintain a cleaner flow all the way to the back of the car, as evidenced by the reduction in size of these "pressure clouds" (iso-surfaces for a total pressure coefficient equal to zero, in case you're asking :) ).

<ImageWithCaption
 src="/assets/images/golf_aero_shield_comparison.jpg"
 alt="Underfloor aerodynamics of the Golf VIII - without and with A2MAC1 aero shield"
 layout="responsive"
 width="1495"
 height="1442"
/>

### The numbers

**The aerodynamic drag on the car was reduced by around 2%** - which is quite significant!
This reduction in drag can be extrapolated to **around 1g of CO2 savings per 100km**. Understandably, car manufacturers constantly need to strike a balance between profitability (the aero shield costs money and hinders maintenance) & emissions (clearly the aero shield helps to reduce emissions) and weight (we're guessing the aero shield would be fairly light). But still, it feels like this would be a fairly "affordable" win in terms of CO2 emissions.

## Conclusion

It's been very interesting to see how we can take a 3D scan of an existing vehicle to then modify it to see the effect on aerodynamics. The results suggest that there is definitely still room for improvement in terms of aerodynamic drag & fuel consumption! Sometimes small changes can have a big (positive) effect for the environment :)

Interesting links:

<ExternalLink href="/partners/engineering/a2mac1">A2MAC1</ExternalLink>
 

<ExternalLink href="/videos/cfd-results-how-to-interpret-an-aerodynamic-analysis/video/XntO27S5Urc">
 How to Interpret an Aerodynamic Simulation Report
</ExternalLink>
 

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

Volkswagen Golf Aerodynamics - How to cut emissions even further

## Introduction

Sometimes the limit to aerodynamic applications is only set by imagination. This time we had the pleasure of speaking to Jay White, Chief Technical Officer at Falcon Pursuit. We have focused on just one of the many fascinating and abstract projects they do in collaboration with the Red Bull athlete performance center.

<ImageWithCaption
 src="/assets/images/profile-picture-jay-white.jpg"
 alt="Jay White - CTO of Falcon Pursuit"
 layout="responsive"
 width="248"
 height="248"
/>

## Extreme Sports and Science Combined

**How does this kind of project come together?**
Surfing came up because as part of the Red Bull performance group, we had just delivered our advanced avatar creation technology, the AVA kiosk to Santa Monica. In these buildings, things are going on that have less to do with delivering drinks, and more about athlete performance groups, e-sports and much more. We were scheduled to work with the triathlete Cameron Wurf and the surf team was also in the building, Ian Walsh being one of them. So, we put Ian into the Kiosk and scanned him in 3D, with and without his wet suit. Asked a few questions about what surfboard he was on currently, to get some basic data to model it.

We found some videos on Ian’s epic big wave ride achieved some months before. The challenge came when we had to model in 3D an ocean wave, which is incredibly dynamic, large and it interacts with the environment in subtle ways. That was the hard part of the story. Once finished, it was a matter of placing Ian’s avatar into the virtual model using 2D broadcast video, snapping his position into the surfboard, and modelling the wave + athlete + surfboard in dynamic 3D space.

<ImageWithCaption
 src="/assets/images/fullwave_Ian.jpg"
 alt="Aerodynamic simulation of Ian Walsh surfing a big wave - image by Falcon Pursuit"
 layout="responsive"
 width="3184"
 height="1901"
/>

**Talk us through the transition from 2D footage to 3D model.**
The process of going from 2D to 3D uses an avatar. The avatar represents the way the athlete looks in space, same shape and even shirt colour. To do so, we “net” the athlete, taking off all the exterior baggy clothing to obtain a skin-tight surface. For a surfer that is no problem as it is basically how he performs naturally when surfing. Having done that, we ran it through our AI ARE (Avatar Rendering Engine), which takes that surface scan and clads it to an avatar adding joints, muscles, eye blink, moveable mouth etc.

Traditionally, this is a multi-day process. In movies for instance, they perform motion cpaturing using mounted sensor balls in 3D space, they hook it to a skeletal structure which in turn gets connected to an animated figure. It is a very long, tedious, high-end & precise engineering process that takes days to complete. Then there are literally hundreds of animators to converting 3D data from the actual actor moving around into a rigged character. All this cannot be done with the surfer since he is out on the wave, and such post-processing effort would be too expensive / slow.

Instead, what the AI ARE engine does is to track Ian in the 2D video footage and matches the 3D avatar to mimic his position. This allows us to model Ian in 3D space based on a single scene. Finer motion and details such as the position of head, fingers, foot and any accessories, is obtained from successive AI solves. Playing with the likelihood of certain positions, the AI does a secondary solve on that to locate such finer details on the avatar.

<ImageWithCaption
 src="/assets/images/avatar1.jpg"
 alt="The 3D Avatar of Ian Walsh on a surf board - image by Falcon Pursuit"
 layout="responsive"
 width="3088"
 height="1901"
/>

The next step is to model the wave itself. For this, we used use Optical Flow. Here's how it works:
Say, for example, I take a picture of a baseball in flight with a normal camera, generally my frame rate is small enough that the baseball blurs only a bit. By taking an image at a high enough shutter speed, it will be super-sharp. By quantifying how much (parts of) images blur (one-thirtieth of a second, one sixtieth of a second image exposure time), you can tell the direction and velocity of that object. It allows us to accurately calculate the velocity for different parts of the wave front. Hence now having both the wave and Ian on a frame, we can calculate aerodynamic drag, hydrodynamic drag and more, based on parameters such as Ian’s velocity, wave velocity, salt content of the wave, air moving past him etc (note: this process has been patented under US patents 9,797,802 and 10,648,883).

## Analysis & Tangible Gains

**I imagine you can quantify lateral forces on the fins, drag coefficients… but how does this translate to actual improvements for the athlete?**
Skilled athletes understand how to look at and interpret their video footage, whether it’s a baseball swing or basketball shot. Taking the example of a gymnast, she goes running down the runway, hits the vault and does a flip. When we have 5 or so videos of successive vaults, we start evaluating and identify which ones were the best.

Adding the 2D to 3D analytics tells us that for the good vault, the hip rotation was 120 degs/s, shoulder rotation was 170 degs/s, centre of gravity and how far the foot hit from the vault when landing. Now having all these facts, we can interpret how shoulders over-rotated, hips under-rotated, and her CG was way far forward. Going back and forth through each simulation, the coach will understand what caused a successful event.

<ImageWithCaption
 src="/assets/images/aero_fins.jpg"
 alt="Hydrodynamic drag analysis on the fins of the surfboard - image by Falcon Pursuit"
 layout="responsive"
 width="3092"
 height="1898"
/>

Now back to surfing, Ian coming across the wave front. His coach points out that in the successful manoeuvre where the wave did not crash upon him, his position was higher on the wave, water was moving a little faster and hence he was moving faster.

By positioning Ian 6 inches up in the wave, he will carry more speed. Evidence suggesting this might be an air current or how the air curves over the top. This software allows us to see where the air is moving in a favourable direction, pushing the surfer. Thus, we adjust the board angle to be in this position in order to have higher probability of a more successful event.

<ImageWithCaption
 src="/assets/images/ian_board.jpg"
 alt="Aerodynamic analysis of Ian Walsh on his surf board - image by Falcon Pursuit"
 layout="responsive"
 width="3240"
 height="1896"
/>

## Simulation Details

**How do you go about the interaction between hydrodynamics and aerodynamics?**
With the more complex simulations, we model both simuataneously. Taking a “bottom turn” as example. When coming down, to go up again you could do a rail slide, a slip, or a flip manoeuvre. For this, the fins need to be in contact with the water, but with cavitation, the board will slip to the side instead of edging. Hence taking that snapshot and running a simulation, we may see that in the last one-sixtieth of a second, the fin went into the water to three-quarters of the way.

Cavitation happens when the fin reaches a certain angle relative to the water stall angle, that instead of slicing though it, bubbles generate in the trailing edge. Hence not contacting water anymore and loosing control.

<ImageWithCaption
 src="/assets/images/pressure_plot.jpg"
 alt="Velocity map of a longitudinal section through Ian Walsh - image by Falcon Pursuit"
 layout="responsive"
 width="3234"
 height="1891"
/>

**From your simulations, what board settings can you change to increase performance?**
Solutions to this cavitation problem where your board is sliding instead of carving across the wave are relatively simple: change the shape of the fin, its length, position and so on. Cavitation is a relatively difficult phenomenon to show and explain to any athlete, but by using scenes and tangible data, you can show how the flow varies from fin A to fin B, highlighting the loss of adhesion with the water.

Hydrodynamics sound very esoteric, normally board shapers come with their magic wand and say: “This is a perfect board for Ian.” After Ian gives it a try, there seems to be a problem with the edge-rails when cutting into the wave. Red Bull Performance Group then comes and demonstrates with a simulation animation that the board is not well suited for him, arguing that it generates too much drag, requires greater flotation and so on. The tough part is that athletes are in love with their equipment; favourite board, position and so on. Asking to change something is monumental. Hence throwing a bit of science behind it will help the athlete trust the path to an increase in performance.

<ImageWithCaption
 src="/assets/images/ian_board2.jpg"
 alt="Flow lines of the air around Ian Walsh - image by Falcon Pursuit"
 layout="responsive"
 width="3234"
 height="1901"
/>

Interesting links:

<ExternalLink href="http://www.dontbeadrag.com/">Don't be a drag</ExternalLink>
 

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

<ExternalLink href="https://airshaper.com/videos/cfd-results-how-to-interpret-an-aerodynamic-analysis/video/XntO27S5Urc">
 How to Interpret CFD Results
</ExternalLink>

Big Wave Surfing - Simulating Ian Walsh's Ride

## Introduction

Mio Suzuki, Sr. R&D Engineer and Aerodynamics Lead at Specialized Bicycle Components gives us an extraordinary insight into how aerodynamic concepts in cycling are brought to live. Starting from the very beginning with fundamental research studies in CFD and wind tunnel testing all the way to optimizing the bike towards a design fit for production.

<ImageWithCaption
 src="/assets/images/profile-picture-mio-suzuki.jpg"
 alt="Mio Suzuki - Aerodynamics Lead at Specialized"
 layout="responsive"
 width="450"
 height="450"
/>

## Historical steps into Aerodynamics

**Who pioneered bike aerodynamics?**
The race that comes into mind when thinking about the first stepts into cycling aerodynamics was the iconic victory of Greg LeMond at the 1989 Tour de France’s last time trial. Unusual for that time, he placed his arms at the center on the aerobar extension instead of the handlebars. His ambition to cut down seconds pushed the engineers to further develop the aerodynamics of the bike. The ”new tech” LeMond used was the triathlon style aerobar extension which enabled him to get into a more streamlined position for the time trial than using a grabbing handlebar. I have no doubt that aerodynamics played a decisive role in LeMond’s win. The bike having that characteristic slanted frame which helped LeMond get into that peculiar position which was indeed intended to reduce aerodynamic drag. I’m not sure if there was any bike frame tech that was intentionally embedded into his racing bike at that time, but what I recall heavily was his use of aerobars.

<ImageWithCaption
 src="/assets/images/greg-lemond-1989.jpg"
 alt="Greg Lemond in aerodynamic position - Tour de France 1989 - Image credit: capovelo.com"
 layout="responsive"
 width="1024"
 height="671"
/>

## Aerodynamic Performance

**Is the bike itself, contributing perhaps 20% of total drag, really that relevant?**
Yes. Especially for the professionals who are competing at the highest level of the sport, a variation in drag within that 20% of the whole system is still big. I am personally in charge of conducting tunnel tests. My main objective always has been to create a meaningful test. Before stepping into the tunnel, I clarify the objectives of the test, so that we can capture the necessary engineering assets which are relevant for the development. Ultimately the question is: can a certain combination of bike, wheel, position… provide a relevant experimental number?

Testing is normally done in several ways. Sometimes bike-only tests (without the rider on top) are used to get a clean number. It is important to realise that the rider is a large bluff body, generating vortices causing vortex-shedding and significant experimental noise. Hence to objectively evaluate if our bike is faster than the competitor bike, it is essential to test the bike only.

More relevant to the rider however is the aerodynamic drag of the full bike-rider combination. To have the rider in the same consistent position, and to allow for proper comparison between tests, we work with Mannequins (dummy models). In the past we had two mannequin positions at Specialized; one for road bike and the other for time trial position. Recently, we added an extra one to reflect differences between male and female bodies.

Besides using mannequins, we perform a lot of athlete testing, at least before COVID-19, with internal as well as professional riders visiting our headquarters to work on their athletic goals.

**Tell me about the aerodynamic design cycle in bikes, the use of wind tunnels, CFD analysis and so on.**
Each manufacturer does it differently. It often starts from the product manager’s specifications for the next bike, which mainly reduces to three pillars; drag, stiffness and weight. I personally like to go hard on CFD from the start, getting numerical drag targets which give me a goal on what to redesign. Then I work with the design engineers, specialists in creating the 3D CAD model. In terms of the workflow, we start with competitor and current model analysis (through CFD and/or wind tunnel testing), where we typically perform at least one wind tunnel at the start of the project to correlate CFD and wind tunnel data.

Once aerodynamics traits and drag reduction requirements are established, we proceed to CFD-based design iterations. These days, using reasonably sized high-performance computing clusters, hundreds of design variations of the initial model can be analyzed in relatively short amount of time. We have partially automated this process by parametrizing CAD models, changing parameters and seeing the effect on drag. With the use of large-scale computing, I have remote access to a cluster set-up with a virtually unlimited number of cores. On these computers, I run about 15 simulations in parallel in a batch and repeat the process as often as I like.

Besides aerodynamics, the role of other physics parameters (weight & stiffness) is very important too. We simultaneously evaluate competing physics/physical objectives, and check if a certain combination of parameters results in the desired bike characteristic.
After this, one or two final prototypes are taken to the wind tunnel to select the winning design and until the design freeze. Once this is done, I am out of the game and the project focus shifts to the manufacturing, where industrial designers turn the prototype into a ready-for-production design. Project design engineers then work with vendors and teams that executes the manufacturing processes.

<ImageWithCaption
 src="/assets/images/specialized-road-bike-windtunnel1.jpg"
 alt="A rider in the Specialized wind tunnel"
 layout="responsive"
 width="1500"
 height="722"
/>

## Future Path for Bike Aerodynamics

**What’s in store for the future? Are we already on the flat part of the improvement curve?**
Not at all! There is still room for improvement. Perhaps not the most drastic changes, but these will likely be driven by an increased understanding of the fundamentals of the aerodynamics. In the past, cycling/bicycle aerodynamic drag heavily focused on manipulating the frontal area (projected area, or the “A” in CdA). But simply reducing the frontal area by making frame tubes skinnier has its limit and will have the consequence on frame structure and weight, as well as influencing the ride quality.

So while paying attention to keeping the frontal area is important, understanding how the frame shape, and bike + rider influences a variation in Cd also becomes the key to create a performance bike that satisfies multiple physical attributes in play for the overall ride experience and rider performance. To do that, my hope is that the community treats aerodynamics as a science and not just only as trendy words. I am hopeful that this renewed industry focus could see a more serious and formal attitude towards the physics of aerodynamics.

<ImageWithCaption
 src="/assets/images/specialized-road-bike-windtunnel2.jpg"
 alt="Cyclists in drafting position in the Specialized wind tunnel"
 layout="responsive"
 width="1367"
 height="934"
/>

**Do you see business moving towards customization of aerodynamics and bike elements based on body features?**
Each athlete’s body features, flexibility and mobility deserve a high degree of attention in time trial. These natural individual differences show up when athletes try to get into time trial position, particularly around the neck and shoulders and in the thoracic spine curvature.
Rather than offering a cookie-cutter approach, tailoring the goods and services to an individual athlete to take advantage of their natural body build makes sense.

Practice like that has been done for many years among the sponsored, professionally competing cyclists, but I think the idea of offering such services is becoming more common in the amateur cycling scene.

**What is the next domain where aerodynamics can be improved?**
I get that question asked very often, but I am selfishly going to keep the secrets to myself!
Computational tools available to the analysis engineers improved dramatically over the decade. Predictive engineering goes on so much beyond trying out simple 2D shapes. DOE, optimization and even statistical/data-driven methods such as machine learning/deep learning can be applied to define design spaces and frame shapes. Since computational hardware is no longer a barrier, adopting the right analysis methods that return large volumes of ride scenarios and relevant results in a timely manner may be the next frontier. There are various ways to approach CFD and experimental aerodynamics that simultaneously explore ride dynamics and frame structure/weight design spaces. I think it’ll be interesting to keep our eyes on how the future innovation practice evolves.

# Insight into Competition

**How are aerodynamics in teams limited by the regulations of competition?**
To be eligible to compete in UCI (Union Cycliste Internationale) races, such bickes must comply with UCI’s bicycle design guidelines. To give you an example, the airfoil aspect ratio cannot be more than 3/1. I personally don’t find the regulations very limiting, there are still rooms for creativity to blossom. On the other hand I feel that reguations on items like helmets can be bit more complex for a perfectly logical reson; they must also comply with safety certification standards. Also the considerations for ventilation comfort are relatively high too.

**How many aerodynamicists work on a single project at Specialized?**
Currently, on the product design, I’m the only one running CFD analysis at Specialized. When it comes to tunnel testing, I have my teammates who can lend hands for successfully completing the tests. It’s always nice to have multiple set of eyes paying attention to every detail during the test. My impression is that most other manufactures also have a similar set up as well.

# Standardising Testing - The Great Debate

<ImageWithCaption
 src="/assets/images/specialized-road-bike-windtunnel3.jpg"
 alt="Performance monitoring during wind tunnel testing at Specialized"
 layout="responsive"
 width="1361"
 height="923"
/>

Towards the end, and interesting debate arose: how standardising testing across all manufacturers could be done. Mio asked us about our thoughts into this topic too.

**_Mio_** – I often hear from customers and journalists about them not able to trust the drag numbers and claims stated by the bike manufacturers because they all claim the title of “world’s most aerodynamic bike”. While I somewhat sympathize with this complaint, to someone like me and knowing that there are other engineers who exercise their best professional practice in conducting these tests and reporting the results, it also came as a bit of a surprise.

What can manufacturers do to earn the customers’ trust?

**_Our response_** - One of the first things to do would be to standardise the testing procedure, which would be similar to what you are doing internally at Specialized. Selecting two or three mannequins, specifying saddle and steering position, frame dimensions and so. Then run them through standardised wind tunnel tests, at a specified speed, yaw angle and so on in order to obtain comparable data. But there is no such standardised procedure yet. Competition teams may do this internally and confidentially by getting competitor bikes and testing them behind closed doors. Precisely behind those doors, every manufacturer has its own opinion on the ideal riding position and the most relevant yaw angle.

The truth is that “the most aerodynamic bike” is different for each race and each rider, so it is difficult to make a global claim like that. In any case, just as we can see in the automotive industry, which is a very mature business, there could be public rankings that fairly compare all designs according to industry standards (although even here we see that manufacturers pull all kinds of tricks to get the official values down). For the bike industry, a crucial question is who would be hosting such comparisons and tests? By all means it must be an independent institution, possibly the UCI, or maybe even an independent simulation service like AirShaper or an independent wind tunnel institute.

**_Mio_** - Ranking based on relative difference might be the best way to go. I have used different tunnels in the US, and I am aware that each tunnel is constructed differently, having different data acquisition instruments. Each tunnel is unique. Although these tunnels have good precisions within their measurements, trying to compare the results in absolute magnitude across different facilities presents challenges. This is because instrumentation as well as post-processing methods can differ among different facilities. Despite this, in general, ranking of the products and trends of drag vs. yaw tend to agree when testing the same object under the same protocol.

Interesting links:

<ExternalLink href="https://www.specialized.com/">Specialized</ExternalLink>
 

<ExternalLink href="https://airshaper.com/videos/sports-aerodynamics-1-winning-the-ironman-triathlon/video/DqlDpUFcScc">
 From 3D scan to Aerodynamic Simulation of a cyclist
</ExternalLink>
 

<ExternalLink href="https://app.airshaper.com/projects/new?accuracy=regular">
 Running your own simulation
</ExternalLink>
 

<ExternalLink href="https://airshaper.com/videos/cfd-results-how-to-interpret-an-aerodynamic-analysis/video/XntO27S5Urc">
 How to Interpret CFD Results
</ExternalLink>

Specialized - How to Design Aerodynamic Road Bikes

## 🙋 About the Author

As a founder and CEO of multiple companies in the field of aviation, drones and other technologies, Lucas Marchesini co-founded <ExternalLink href="https://www.formulaairgp.com/">Formula Air Grand Prix</ExternalLink>, with Cristian Mendez Carmona (who is the CEO) and other ex-colleagues. Now he leads <ExternalLink href="https://www.mantaaircraft.com/">Manta Aircraft SA</ExternalLink> which is developing the ANN2, the hybrid-electric V/STOL race plane that will be used for the series!

## 📢 Formula Air Grand Prix

In the near future, new ways of transportation are likely to be added to the mix Urban Air Mobility (UAM). The key promises of this upcoming way of moving people and goods in the larger cities are fascinating: faster travel at reasonable fares; safe and enjoyable flight experiences; and smoother integration with the other transport modes. This can't be done with the existing helicopters and airplanes, therefore new aircraft types are being designed and developed.

<ImageWithCaption
 src="/assets/images/formula-air-grand-prix-illustration.jpg"
 alt="Aircraft racing in the Formula Air Grand Prix series - Illustration by Formula Air Grand Prix"
 layout="responsive"
 width="1771"
 height="698"
/>

The Formula Air Grand Prix (FAGP) is a global air racing competition aimed at bringing
the stakeholders of this industry together, giving them a platform to showcase their
technologies to a larger and larger audience. As in many other disciplines, racing
competitions are an effective way to foster advancement in technology. FAGP's goal
is to accelerate the market entry of the best players in the industry.

Manta is developing the base aircraft for the series, the Manta ANN2. This, in turn, can be modified by the teams with the aim to improve its competitiveness. The development of the Manta ANN2 aircraft goal is to demonstrate the capabilities of a vehicle conceived as a HeV/STOL. That's H for Hybrid, e for electric and V/STOL for Vertical or Short Take-Off and Landing. In practice, it can take off and land vertically like a helicopter, and fly horizontally like an airplane.

One of the goals of the project is to make an aircraft with exceptional maneuvering capabilities resulting from this mix of airplane and VTOL characteristics: hover in midair; perform a backward flip; jaw and roll beyond what standard flight control surfaces – such as elevators, ailerons and rudders – would allow.

## 🌬 Propulsion layout

<ImageWithCaption
 src="/assets/images/manta-an2-2.jpg"
 alt="The propulsion layout of the Manta ANN2 Formula Air Grand Prix aircraft in VTOL mode - Illustration by Formula Air Grand Prix"
 layout="responsive"
 width="1063"
 height="839"
/>

The propulsion layout is the result of a series of logical design choices:

- During take-off and landing, all the propulsion is needed to provide the vertical thrust that lifts the aircraft. By contrast, in horizontal flight, the propulsion needed is just a fraction of that thrust, as the remaining force comes from the aerodynamic lift produced by the wings. If you use the same thrusters in both modes, then they'll be working at around 15-20% of their maximum power for most of their life (remember that these aircraft are meant to spend 95% or more of their flight time as airplanes, and less than 5% as VTOLs).
- Using propellers, or any other form of "thruster" for vertical lift, means that they need to operate at high power for a short time. As this is the most demanding flight regime, you're obliged to optimize the propeller blades for vertical take-off and landing, leaving them less than optimal for other flight regimes such as mid- and high-speed horizontal flight. One option is to change the angle of the propeller blades depending on the flight regime (variable pitch props). This would require extra mechanical components that increase weight and also require more maintenance as well as spare parts in stock.
- The most reasonable solution is to choose a design point for the thrusters that falls somewhere in between the static and cruise conditions, with the effect of losing thrust in the demanding VTOL situation.
- To maintain the capability of vertical take-off and landing, additional thrusters are required. These can remain concealed in the fuselage during the winged flight to reduce drag in horizontal flight. And as they are of help only during take-off and landing, they can be fully optimized for such high-power static conditions, increasing efficiency in VTOL flight. The other thrusters, in contrast, are optimized for higher efficiency in horizontal flight mode.

<ImageWithCaption
 src="/assets/images/formula-air-grand-prix-1.jpg"
 alt="The Manta ANN2 Formula Air Grand Prix aircraft in VTOL mode - Illustration by Manta Aircraft SA"
 layout="responsive"
 width="603"
 height="339"
/>

## ✈ Aerodynamic Layout

<ImageWithCaption
 src="/assets/images/formula-air-grand-prix-2.jpg"
 alt="The layout of the Manta ANN2 aircraft features a large canard setup - Illustration by Manta Aircraft SA"
 layout="responsive"
 width="603"
 height="339"
/>

The aircraft features a canard layout, with the pitch-control plane set in front of the main wing (traditionally, these surfaces are in the tail). This provides the following advantages:

- All the surfaces generate lift, thus increasing efficiency in cruise
- The Centre of Gravity is located between the two lifting surfaces, which is necessary to have the position of the fuselage thrusters in the bow and stern of the airplane
- A concentration of the most important structural components such as the wing-fuselage intersection, engine bay and main landing gear, thus reducing the structural weight, in comparison with having them dispersed along the fuselage
- A large part of the fuselage is kept free from the aerodynamic disturbances of engine air inlets and outlets
- A wide lateral angle of downward view for the pilots, which is particularly useful in the surveillance and search missions (and also in racing competitions)
- In terms of maneuverability, canards of this substantial dimension offer quick response in pitch and, through differential rotation (a difference in angle of attack between the canard wings), a fair contribution to the roll control power.

The positioning of the ducted fans underneath the main wing, ahead of the flaps, also provides advantages:

- The lifting performance of the main wing is increased at low speed, especially during short take-off and landing. Exploiting the "vectoring" of the wing thrusters increases the maximum take-off weight, allowing the aircraft to launch on short semi-prepared airstrips.
- As in every canard configuration the effect of the forward surface ('front wing") on the rear main surface ("main wing") is not negligible, in the adopted configuration, the presence of the large wing fans in front of the wing helps decreasing this effect. This is optimal in cruise.

## 🔌 Power Management

The Manta ANN2 features a hybrid propulsion system: a gas turbine running an electric power generator, batteries and electric motors. This configuration reduces size, weight and cost. The turbine allows increasing cruise range, as it is used to recharge the batteries during cruise flight (or at idle on the ground, eliminating the need for a recharging infrastructure). For VTOL operations extra energy is sourced from the batteries, and that’s when the max turbine power output is required.

## 🖥 Design Tools

<ImageWithCaption
 src="/assets/images/formula-air-grand-prix-3.jpg"
 alt="CFD (Computational Fluid Dynamics) analysis of the Manta ANN2 Formula Air Grand Prix aircraft - Illustration by Manta Aircraft SA"
 layout="responsive"
 width="603"
 height="307"
/>

Manta is following the fully simulated aircraft design approach, from the flight dynamics – through the use of Computational Fluid Dynamics (CFD) and wind tunnel data – to the different onboard systems (propulsion, electric, flight controls, etc.), being all integrated into a real time pilot-in-the-loop simulator. CFD have been extensively applied to analyze and optimize the pressure patterns on the aircraft, to obtain crucial inputs on lift and drag forces, and pitch, roll and yaw moments for the controller. And so on.

## 💡 Conclusion

Formula Air Grand Prix will be a fascinating playground and testbed for the upcoming technologies that will eventually make their appearance in the Urban / Regional Air Mobility scenery. Novel aerodynamic layouts, propulsion setups and drive train packaging will contribute to make it become a sensational sport!

Interesting links:

<ExternalLink href="https://www.formulaairgp.com/">
 Formula Air Grand Prix
</ExternalLink>
 

<ExternalLink href="https://www.mantaaircraft.com/">
 Manta Aircraft SA
</ExternalLink>
 

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

Formula Air Grand Prix - Racing in the Sky

## Introduction

During this interview, we had the pleaseure of talking to Dominic Harlow, Motorsport Engineer with a wide backround in F1 sport. His passion towards motorsport and enthusiasm towards engineering have alowed him to be involved in many interesting projects throughout his career.

<ImageWithCaption
 src="/assets/images/profile-picture-dominic-harlow.jpg"
 alt="Dominic Charles Harlow"
 layout="responsive"
 width="318"
 height="422"
/>

## And It's Lights Out & Away We Go

**Tell us about yourself and your career path?**
I’ve been involved in motorsport a long time, it’s where I have always wanted to take my career. When I arrived in F1, I started to work in data engineering at the track, performance engineering and vehicle science. A little bit of design work as well. In F1, at that stage with the great proliferation in use of simulation tools, lap simulation particularly, data acquisition and analysis tools, teams had quickly realised the importance of aerodynamics as the primary performance driver for the cars they could influence. So, as has always been the case, many years before I ever got involved, the aerodynamics were fundamental for the performance and were what really differentiated in the largest part between the teams. Thus, it is easy to understand that it is something which interested me a great deal, involving myself with the team in this respect. F1 is unique in the amount of aerodynamic development effort that a team expends, much more than what you find in any other formula. It is even multiple times the effort OEMs put into launching a new model. If you just look at CFD and wind tunnel hours F1 is doing far more work than an OEM does, in a single team and on a short period of time.

<ImageWithCaption
 src="/assets/images/formula-one-cars-on-track.jpg"
 alt="Australian Grand Prix - Melbourne 2014"
 layout="responsive"
 width="3267"
 height="2174"
/>

## Thrive, Don't Just Survive

**How is aerodynamic testing embedded within the design cycle of a car? Do you start with a clean sheet or do you iterate upon previous designs?**
It is a constant interplay between both. There is always a debate in F1 (and motorsport in general), when developing a car on whether to think of new concepts or to optimize the existing one. Dreaming up the latest and greatest designs for a car will allow you to unleash new areas of performance. Afterwards, you can evaluate how much should you continue pushing your existing avenues of development and iterate towards better solutions. Usually the iterative approach wins out against the complete reinvention of a new concept. But one cannot underestimate the importance of starting with the right concept, fundamentals and layout for car, so that you don’t force the iteration into areas that are not fruitful or where the ultimate performance is limited. The third aspect that comes into play are the regulations: just like the cars, the regulations become increasingly complex, so they place additional constraints on the development process and the car concept, and they change from time to time. Thus, they force you to rethink, to abandon certain areas and come up with new ones.

**When you start the design cycle of a car, is aerodynamics positioned as the top priority?**
Aerodynamics do dominate conversations in F1, as does the power unit. In terms of chassis design, it is more of an integration task. It goes without saying that the power unit supplier is the one in charge of delivering maximum efficiency and good energy recovery. So, for the chassis designer, aero comes first. Tyres (and tyre management) and all the other aspects around that are next, along with good power-unit integration.

Additional research is performed to optimize structures and reduce weight. Satisfying the safety criteria (which thankfully continue to evolve) also requires quite a lot of effort. And the teams are always looking for improvements in stiffness and structural integrity. All the teams improve year on year, so not paying attention to a certain aspect will have you lose competitiveness.

<ImageWithCaption
 src="/assets/images/formula-one-chassis-model.jpg"
 alt="Formula One Chassis Model"
 layout="responsive"
 width="870"
 height="732"
/>

## Simulations & Testing

**With regards to the simulations, how are aero mappings tested, are these done altogether with other suspension tuning or chassis adjustments?**
Almost all simulations involve a full model of the car (masses, suspension data, tire data, ...) and the aero map is one of the crucial elements in such a model. The higher the fidelity of the aero map, the more reliable the results of the complete simulation will be (like lap time simulations for example). It all depends on what aspects of the performance you are looking to focus on. Once you have the model, you can play with the inputs and evaluate the changes in the output.

<ImageWithCaption
 src="/assets/images/formula-one-cfd-total-pressure-coefficient.jpg"
 alt="The total pressure coefficient obtained through CFD simulation"
 layout="responsive"
 width="1795"
 height="919"
/>

**Could you give an idea of the volume of CFD work done behind these cars?**
It is difficult to quantify the exact number of simulations done; it depends on how you define a simulation. There are so many recipes and methodologies applied to F1 CFD from the smallest sub-models of parts of the car to fully unsteady simulations at complex attitudes. And things get even more challenging when simulating multiple cars in order to better understand the wake and its effect during close following. How many of those you do depends on the size of the simulations, but you might see around 30,000 a year per team. By regulation the teams can only use a certain amount of resources to apply to elements of testing, thus it is constrained. It is still an intensive level of research and the balance between wind tunnel and CFD is now clearly leaning towards CFD as it becomes more and more available and efficient.

**You have been working as a race engineer. From that position, have you seen a change in attitude towards aerodynamics from driver’s side? How big is such awareness of the importance of communication with engineers?**
The drivers certainly learn and develop in the same way teams do - as the team’s understanding grows, that becomes embedded in the drivers. The drivers do understand from early stages of their careers, that they have to speak the same language as the engineers. That way, they can help the engineers understand where certain aspects of the behaviour of the car are coming from and how those might be aerodynamically driven. A good driver that is aware of this will be able to speak to the team and help them develop a better understanding of the aerodynamics of the car. Also, they are heavily involved in the simulations back at the factory (like driver-in-the-loop-simulations), discussions with the engineers on concepts for the new car, ... giving feedback on setup & pointing out areas for improvement on the car.

# F1 Future - Straight Line or Not?

**Let's talk about the new regulations, which constrain the aerodynamic development of the car. How do you see the future for F1?**
For F1 as a sport, I certainly see a strong future - it has all the elements of a great sport and spectacle. It is unique in that it combines the individual brilliance of the driver along with teams and engineers. A spectacle in all its essence with huge events at each Grand Prix, touring all around the world.

From a technical and regulatory point of point of view, it is also about efficiency and a real-world challenge. There is nothing in life that is not constrained by what’s available. I think the sport is relevant, in terms of the mobility strategy, and certainly there is still an element of internal combustion engine innovation and trickle down of technology to the public. As long as things like sustainability & entertainment have been kept in mind, I think everything that has been decided upon is for the good of the sport.

<ImageWithCaption
 src="/assets/images/formula-one-fernando-alonso-malaysian-grand-prix.jpg"
 alt="Fernando Alonso - Malaysia GP"
 layout="responsive"
 width="1024"
 height="670"
/>

**As for the upcoming change in rules, what is the next big aerodynamic point of innovation in F1?**
The biggest changes will come in 2022, with the introduction of new regulations (based on development work that has already been done). Certainly, it will be interesting to see how this 'reset' plays out after all the progress that had been made on the current cars & the success of that philosophy. Engineering is a continuous process, new things are built and continue to evolve - so we may have to wait a few races to gather enough 'sampling points' before drawing conclusions on the success of the new regulations. Coupled with that is the change of tyres which is a huge thing aerodynamically.

**Any other thoughts?**
I am certainly very interested to see the development of CFD and HPC as it applies to motorsport over the course of the coming years, to look how it is delivered and made available; on-premise, cloud, as open source or vendor code, exploring different workflows and applications.

Interesting links:

<ExternalLink href="https://dominicharlow.com/">
 Dominic Harlow Consulting
</ExternalLink>
 

<ExternalLink href="https://airshaper.com/videos/race-car-aerodynamics-3-aero-mapping/video/u-GyTRblNmc">
 Aero mapping for race cars
</ExternalLink>
 

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

<ExternalLink href="https://airshaper.com/videos/cfd-results-how-to-interpret-an-aerodynamic-analysis/video/XntO27S5Urc">
 How to Interpret CFD Results
</ExternalLink>

Formula One Aerodynamics - An Interview with Dominic Harlow

## Introduction

On this occasion, we've had the chance of speaking to one of the engineers in charge of designing sailboats for two of the toughest and most prestigious sailing competitions of all times; the Volvo Ocean Race and the America's Cup. Britton Ward, Vice President of Farr Yacht Design has given us some thought-provoking and fascinating insight into the aerodynamics of sailing.

<ImageWithCaption
 src="/assets/images/britton-ward.jpg"
 alt="Britton Ward"
 layout="responsive"
 width="2000"
 height="1214"
/>

## Setting sail towards a Childhood Dream

**To put things into context, talk me through your career path and how you got into this industry?**
My name is Britton Ward, I'm Vice President and Senior Naval Architect at Farr Yacht Design in Annapolis Maryland, USA. My fascination with sailing yachts happened at a young age. Growing up in Western Australia I was completely enthralled by Australia II's America's Cup victory in 1983. The 1987 Cup defence was in my home Fremantle waters and from that point on I knew I wanted to be involved in designing racing yachts. I attended the Webb institute of Naval Architecture in New York and followed that with a master's degree from MIT. From MIT I joined Farr Yacht Design and have been lucky enough to work on a wide range of projects including 4 America's Cups, Volvo Ocean Races, grand-prix racing projects, cruising boats and a number of high-performance powerboats.

## Aerodynamics in Yacht Sailing

**Throughout these years have you seen a significant change on the aerodynamics side of competition?**
Yes, what makes sailing design so unique is that we have to operate across such a wide range of operating conditions; from no speed to 30,40, sometimes 50 knots, upright and at heel and at different angles of sideslip or leeway. The designs must work across a really broad range of conditions which makes simulating every aspect very demanding. The second part is that we are in perhaps the ultimate efficiency game, trying to maximize aerodynamic drive forces while remaining always on a quest for minimum hydrodynamic drag. So, we are constantly trying to improve both the hydrodynamic and aerodynamic sides of the performance equation. Given water density is 800 times that of air, we work really hard at hydrodynamic optimization trying to reduce drag but the sails are our engine and so improving aerodynamic drive and minimizing aerodynamic parasitic drag is critical to achieve maximum efficiency. We work with sail designers in analysing sail shapes and we put a lot of effort into reducing windage by shaping hull and deck surfaces. At the highest end, in America's Cup programmes we have looked at the effect of having a rope in front of the mast for the windage gain or shaping of bowsprit sections to achieve aerodynamic driving force. With the recent push into hydrofoiling yachts that achieve speeds of 40 to 50 knots, the importance of reducing windage drag has become ever more critical and is getting a lot of focus.

**In terms of all these features and challenges you have tried to improve, tell me about the design cycle of these sailboats.**
The challenge is whether the team can support enough R&D to do multiple design refinement cycles using high fidelity tools; whether that be tow tanks or wind tunnels or CFD. For a lot of our regular designs the design budgets and timelines can't support unlimited research, so we work to leverage our existing databases, use empirical methods and perhaps validate with some limited simulations.
Whether it is empirical models or experimental data or simulation results, we use different techniques to build Response Surface models that characterize the hydrodynamic and aerodynamic forces acting on the boat, appendages and sails across the range of operating conditions. These models are then used to predict the performance of the boat using a Velocity Prediction programme that can be either 'steady-state' or for very high end projects a full time domain simulator that allows the boat to be sailed virtually. We can then couple that information with expected race conditions or race simulations and begin to optimize the design for the targeted conditions.
We have invested heavily in an automated design analysis system called IDEOS that brings together a lot of these elements and automated shape morphing and generation to allow us to look at 1000's of design options before committing to final design.
Even with the most complex simulations and computing we are a long way from a black box design process. Anything the computer spits out needs experienced eyes that understand both what's 'under the hood' in the codes but also appreciates real life sailing complexities that aren't able to be fully captured in models.

<ImageWithCaption
 src="/assets/images/Vo65Hydro.jpg"
 alt="VO 65 (Volvo Ocean) Pressure Mapping"
 layout="responsive"
 width="1043"
 height="930"
/>

**With regards to quantifying and modelling the interaction of different components, what impact does the pressure difference from the main sail have on the entire aerodynamics of the boat?**
Like in most industries, one starts with computationally simple things, just analysing a set of sail geometries in the air without the presence of the mast, rigging, hull etc.. For sailing at low apparent wind angles with minimal separation we can use Vortex Lattice or Panel methods but at wide angles with spinnakers we have a much more complicated flow regime requiring RANS and in some cases DES simulation to properly capture the flow. Modelling only the sails misses the interactions with mast, rigging, hull and deck which can have a really big impact on the forces and the flow field physics.
Much as with hull hydrodynamics we always want better and better accuracy but also need to run a lot of operating conditions to properly model how forces change in different conditions. Every design team needs to find the right balancing act here that can capture as much physics as possible but provide enough data to answer the design questions.

<ImageWithCaption
 src="/assets/images/WindTunnel1.jpg"
 alt="Wind Tunnel Testing on a sailing boat."
 layout="responsive"
 width="479"
 height="639"
/>

**To what extent is it worth developing these foiling sailboats if cavitation effect comes into play at high speeds?**
The shift to foiling sailboats has dramatically changed the performance zone for these types of boats. Hydrofoiling is not new but the advent of advanced materials has allowed us to achieve exceptionally light weight and strong boats that can be lifted clear of the water by hydrofoils even in quite light conditions.
At a basic level hydrofoil design is the same as airfoil development but we are operating in a much more dense fluid. With the foils supporting the boat the total drag is reduced dramatically as the hull is now in the air and so aerodynamic efficiency becomes even more critical.
At the higher speeds the low pressure on the foil can drop below the vapor pressure of water cause the water to 'boil' or cavitate and this phenomena tends to govern the upper end of the speed range. Its fundamentally related to the pressure at the foil and the minimum pressure coefficient, if that exceeds the vapour pressure, the water boils. The question is, how do we reduce that? Generally, a bigger foil will have a lower loading on it, which will delay cavitation, but it also has more drag. You are kind of flirting on that cavitation edge or looking for solutions that are somewhat benign to cavitation.

<ImageWithCaption
 src="/assets/images/streamlines.jpg"
 alt="Bottom view of the hull with hydrofoils showing surface pressure & 3D streamlines."
 layout="responsive"
 width="3443"
 height="1217"
/>

# Essence of Competition

**Are there any limitations dictated by competition or regulations that limit aerodynamic design freedom?**
Yes, in America's Cup, for the current AC75 specifically there is a rule that governs the parameters of the boat in a similar way to Formula1. These rules control dimensions, materials and construction processes and the number of components of different types that can be built. It also prescribes limits on control system etc. In the current rule it precludes the use of towing tanks and wind tunnels, requiring design optimization to be completed using only simulation-based analysis.

**I see that there is a strong similarity to F1 sport. Recently F1 has been forced to prove itself useful for the general industry, have you felt that there is the same sort of pressure on America's Cup?**
Everyone involved feels that there must be some trickle down of technology to the average sailor, and there is always a big debate about how much technology will trickle down from the current America's Cup boats. There are certainly a lot of design processes and tools that can be immediately applied to all manner of boats. Refinements in deck hardware and mechanical systems always feed into a range of boats.

**How many engineers are dedicated to aerodynamics within the teams?**
Every company organises itself in different ways so the way we are structured is probably a bit different to other companies or teams. Depending on the scale of the project we would typically have dedicated one or two guys to the aerodynamics in general, and one of those may be heavily involved in the sail design area. Fundamentally the hydrofoil is an airfoil wing, even if it is operating in water so all of the aerodynamics expertise is directly relevant and we use a lot of the same tools and methodologies. In our team we have often had naval architects working with aerospace engineers and I always find it is important to cross-pollinate from different disciplines.

# Iconic Designs

**Tell us what is so special about the VO65?**
VO65 was designed for the Volvo Ocean race, which is a fully crewed race around the world race. The VO65 is a one-design boat in which each of the boats are as identical as possible. This was a big change from prior races where they utilized a design rule and each team employed designers and sought to find a design edge. In the 2011-2012 Volvo Ocean race the boats were designed to the VO70 rule and there was a lot of design freedom but also a tendency to push the limits which resulted in a lot of breakages.
Thus given the economic situation and the issues in 2014 the race organizers felt that best option to insure the future for the race was to have a fleet of absolutely identical boats and we were commissioned to design the VO65. The main directives for us were to make the boats robust and reliable, as identical as possible. We sought to get as much performance as we could but without sacrificing those core factors. There was limited amount of budget for research and simulations which we utilized to explore some appendage options and develop refined performance predictions. We utilized our internal methods to refine the boats windage characteristics but were not able to complete a lot of detailed aerodynamics refinements. We worked closely with the sail and mast design teams in the sizing of the rig and selection of sail sizes, trying to develop the sail wardrobe to be as solid as possible.

<ImageWithCaption
 src="/assets/images/volvo-ocean-race-yacht.jpg"
 alt="Volvo Ocean Race Yacht."
 layout="responsive"
 width="1400"
 height="350"
/>

**This was back in 2012, but what are the main areas of improvements currently in 2020?**
The next ocean race will start in 2022, having two classes, the VO 65 and the IMOCA60. Much like the older VO70 rules, the IMOCA60 is a development class, having a core set of rules but allow a lot of design freedom. The boats are now employing hydrofoils as well which has resulted in large performance improvements. In this case, they are not fully airborne as in America's Cup boats, but the foils lift most of the hull clear of the water so are perhaps better seen as 'foil-assisted' boats.

# Technical Insights

**What is the actual difference between foil assisted and fully flying?**
Primarily, the IMOCA60 is not allowed to have a tail elevator, so there is no T-rudder, and it uses passive hydrodynamics to maintain 'stable' flight. A big push in that design space is both on sizing and placement of the foils, and in developing a pitch-stable boat across the speed range that while still meeting all the stability and safety rules for an ocean going yacht. The IMOCA60 is an exciting design arena right now as there are a lot of areas to explore and optimize; how much stability you need from the hull design, from the appendix, keel or bulb, the size of the foils; There is plenty of room for a big leap forwards, since there is so much latitude to explore, but typically these budgets are much smaller than America's Cup ones so you have to have bright people and a good understanding of the constraints to make an improvement.

**You previously mentioned pitch-wise stability, are there any similarities to the oscillatory modes present in aviation?**
Yes indeed there are, in aeroplanes it is the phugoid mode, in powerboats we call it porpoising and it is a dynamic instability. A lot of work has been done in the power boats along the years to understand what characteristics of a hull shape make it more or less susceptible to porpoising. Much like an aeroplane, the position of the centre of gravity relative to the hydrodynamic centres is an important part of it. When we come to foil assisted sailboats, this gets even more complicated as we have the extra influence of the hydrofoils changing the boats attitude and varying dynamically with speed. Even in some of the initial simulations I have been doing in the last 6 months with some of my team, we have seen some configurations which appear to be pitch unstable and requiring a bit of trial and error, to understand the right combinations of running trim, foil sizing and placement and centre of gravity position. Now we are coming up with a design methodology using lower fidelity simulation methods to give us immediate guidance on whether a particular design configuration is going to be stable or not.

<ImageWithCaption
 src="/assets/images/AC75.jpg"
 alt="AC 75 - Richard Gladwell, Sail-World.com/nz."
 layout="responsive"
 width="2407"
 height="1354"
/>

**Does the actual position of the crew significantly impact the aerodynamic efficiency and separation points?**
In any of our designs we focus on crew placement, for their center of mass impact, their ability to ergonomically complete their tasks and for their impact on windage and aerodynamics. Depending on the size of the boat, the weight of the crew has a big impact on the stability of the boat. A smaller boat, the crew weight is a much larger proportion of what the entire boat is, then thus greater impact on resisting the sails and tipping the boat over, therefore you automatically have a trade-off between aerodynamics and crew righting moment.

When you get to a boat like the AC75, the speeds have gone up so much, the aerodynamic impact of the crew is even more significant while the impact of the crew weight on stability of the boat is much smaller. As a result, we see the crew essentially 'buried' in tunnels with their heads down to be as streamlined as possible.

# On Course for a Bright Future

**What are the projects you have in mind in the near future?**
We are marching down this path of hydrofoils, not just for racing, but also for cruising boats. We recently launched 142-foot cruising boat with a 9-meter Dynamic Stability Systems hydrofoil. The addition of the foil improves performance and reduces heel angles by up to 15+ degrees while improving pitch motions which dramatically improves crew comfort. I think we are seeing other avenues where these technologies can be applied. Placing a foil in a 142-foot superyacht was a big challenge and one of the hardest projects we have done recently. This was a sliding foil, one foil works on both sides, so it has to be actuated and pulled in to the boat and put out the other side, when the boat tacks. Because this boat will sail the globe we needed to do a lot of assessment of damage possibilities to ensure the boat would be safe in the event the foil collided with something.
On a simulation front I am always trying to utilize more simulation tools in all of our designs. Recently we have done a lot of work with OpenFOAM, also Numeca's Fine/Marine primarily for hydrodynamic simulations. We also make a healthy use of panel methods and vortex lattices, X-Foil and XFLR5, depending on the types of problems we are looking at. Since we need so much data in order to make an informative design choice we are always trying to balance fidelity versus run-time. Just running one point of one geometry teaches us very little, so we are constantly looking at ways to use advanced statistical fitting techniques to make the most value out of the data we get from simulations and apply it to broader answers. Beyond that, we have been putting a lot of focus into the automation of design cycles; all the way from geometry morphing though to meshing to running simulations and post processing.

<ImageWithCaption
 src="/assets/images/DSS_Baltic142_Canova.jpg"
 alt="ABaltic 142 Canova"
 layout="responsive"
 width="1246"
 height="815"
/>

Interesting links:

<ExternalLink href="http://www.farrdesign.com/">Farr Yacht Design</ExternalLink>
 

<ExternalLink href="https://airshaper.com/videos/airbus-talks-part-3-of-4-americas-cup-aerodynamics/video/ZcD9iA9DPrI">
 America's Cup Aerodynamics - Interview with AIRBUS - Part 1
</ExternalLink>
 

<ExternalLink href="https://airshaper.com/videos/airbus-talks-part-4-of-4-americas-cup-aerodynamics-part-2/video/AdGuENBuZ-Y">
 America's Cup Aerodynamics - Interview with AIRBUS - Part 1
</ExternalLink>
 

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

Sailing Yacht Aerodynamics & Hydrodynamics

## 🙋 About the Author

For many years, Benjamin worked in research and development of turbomachinery applications for ABB. Optimization using CFD (computational fluid dynamics), heat transfer and fluid-structure interaction were important topics at that time. Since 2014 he is partner at Swiss company <ExternalLink href="https://www.streamwise.ch/">streamwise GmbH</ExternalLink> and is one of the core developers of their ProCap system, a tool for 3D real-time velocity measurements (around objects in a wind tunnel for example).

## Acknowledgements

Racecar geometry images and CFD-Results courtesy of Academic Motorsports Club Zurich (AMZ) from ETH Zurich, Frank Schaufelberger.

## The Aerodynamic Design Cycle

An aerodynamic design cycle is typically structured as follows:

- Concept: the creation of design ideas based on certain fluid hypotheses that can theoretically provide improvements. These concepts are then translated into digital 3D models and/or physical prototypes.
- Verification: this is where the flow around the new design is analysed to verify the hypothesis of a design.
 This can be done through CFD simulations and/or wind tunnel testing and/or real-world testing.
- Optimization: based on the results, the design is modified.

This cycle is then repeated until the defined goals have been reached. Here's an example:
The drag of a wing can be reduced by lowering the curvature (design idea) such that the separation zone is decreased (hypothesis). In a situation where a modification (curvature change) does not provide the desired result (drag reduction) as expected, the engineer must verify the flow topology and search for reasons, then improve the hypothesis and the design.

Over time, the majority of verifications are done through CFD: codes have become more accurate, computers have become more powerful. But sometimes CFD is not able to capture certain real-world effects, or it would be prohibitively expensive/time-consuming through CFD. In such cases, wind tunnel tests are the preferred verification method. But in a wind tunnel, it is much more difficult to visualize the flow and thus more difficult to verify & improve the hypothesis. This is what we call the verification gap: you have the real flow in front of you, but you cannot see it.

## Closing the Gap

In such a situation it is not uncommon to fall back on the good old smoke probe or tufts as a measurement tool. Although very easy to set up, these methods provide only limited and purely qualitative information to the operator (they show the direction of the flow, but not the magnitude). And because the smoke itself is an aerodynamic phenomenon, it is difficult to compare this to CFD results.

High-tech PIV (Particle Image Velocimetry) systems are also on the rise - they use lasers to scan the flow speed & orientation in 2D planes. Fantastic technology, but they have the disadvantage of being very expensive and dangerous for humans.

<ImageWithCaption
 src="/assets/images/eth-zurich-procap-wind-tunnel-live-measurement.jpg"
 alt="3D flow measurement around the car using a probe & tracking system."
 layout="responsive"
 width="1669"
 height="1100"
/>

The idea behind the ProCap (Probe Capture) flow measurement system is to close this gap:
Keep the intuitive handling of a smoke probe but at the same time provide accurate, quantitative measurement data visualized in real time.

The region of interest is manually scanned by the operator using a hand-held probe while the system optically tracks the probe’s instantaneous position, records the probe data, and visualizes the flow field in real-time. This allows to map out the effect of a design modification quickly and the assessment of the 3D flow data can start at the time of the measurement. The quantitative dataset can be lined up against wind tunnel data or compared in detail with CFD data.

## Case: Formula Student Electric - ETH Zurich

One of the cases where real-world effects play an important role are race cars:
The exact shape of edges and corners, the vibration of the structure, the surface roughness of a leading edge, the deformation of a wing due to aerodynamic loads: all these details are difficult to get right in CFD but can have a substantial influence on the flow and the overall performance. At the same time, due to the complex geometry and flow topology, flow measurements are difficult.

<ImageWithCaption
 src="/assets/images/eth-zurich-procap-wind-tunnel-test.jpg"
 alt="The ETH Zurich AMZ Racing eiger race car in the wind tunnel setup with moving belt."
 layout="responsive"
 width="1841"
 height="564"
/>

AMZ Racing from ETH Zurich, a former winner of the competition, optimized their _eiger_ car in the wind tunnel using the ProCap system. Although we cannot show too many details and unveil secrets here, we can provide qualitative insight into the measurement data and how it helped to close the verification gap. The measurements took about 5 hours in total for all runs (including setup changes). The team also performed CFD simulations (CFD data shown are from DES (detached eddy simulations) averaged over 1.2 seconds physical time) prior to the wind tunnel tests, so a comparison between the two data sets was possible.

<ImageWithCaption
 src="/assets/images/eth-zurich-procap-slices-location.jpg"
 alt="Complex flow patterns like the trajectory of vortex cores can be measured and compared to CFD data."
 layout="responsive"
 width="1715"
 height="890"
/>

The image above shows the location of 3 exemplary visualization planes from the entire measured 3D data set. It is interesting to see the location of the tip vortex from the upper nose wing, which is important since this vortex is designed to bring high energy flow to the rear wing of the car to generate as much downforce as possible.

In the images below, the total pressure coefficient (colour map) and streamlines (pattern) are shown for 3 planes around the front wing for both CFD and measurement data. While the overall flow topology matches very well between measurement and CFD data, some discrepancies can be found e.g. in the positions of the vortex cores or the sizes of the low-pressure zones, etc. Using 3D measurement data it was possible to locate these discrepancies between CFD and reality.

<ImageWithCaption
 src="/assets/images/procap-sections.jpg"
 alt="The total pressure for the 3D different planes (left: CFD // right: wind tunnel)."
 layout="responsive"
 width="697"
 height="1060"
/>

## Conclusion

Measuring velocity vectors & magnitudes in 3D by freely moving a probe makes it easier to understand the complex flow structure around a race car.
Overall results match very well with CFD findings, and local discrepancies provide an indication as to where real-world effects might play an important role.

Interesting links:

<ExternalLink href="https://www.streamwise.ch/procap/">
 streamwise Procap
</ExternalLink>
 

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

<Link href="/videos/cfd-results-how-to-interpret-an-aerodynamic-analysis/video/XntO27S5Urc">
 <a>How to Interpret CFD Results</a>
</Link>

3D Flow Measurement in the Wind Tunnel - A Formula Student Case Study

## 📢 Introduction

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._

## ▶ The Aerodynamic Design Brief

The last evolution of the successful Mitsubishi Lancer to take part in the World Rally Championship (named as WRC04 and WRC05) included one of the most developed aerodynamic designs of the moment. We went in for a close review of its aero design and performance, together with the Ralliart Chief Engineer Roger Estrada and one of the official drivers of the team in 2004, Kristian Sohlberg. They both kindly accepted to answer our questions about the car.

<ImageWithCaption
 src="/assets/images/mitsubishi_WRC04_1.jpg"
 alt="G.Galli/G.D’Amore, Mitsubishi Lancer WRC04, Rally Catalunya, 7th – pictures by Mitsubishi Motorsport Corp."
 layout="responsive"
 width="1421"
 height="593"
/>

The design process of the WRC04 started in early 2003, and aerodynamics was one of the areas in which most efforts were devoted. In order to know first-hand details about the aero design, we contacted Roger Estrada, who gently accepted to share with us many details of the design process. Estrada (ex-Seat Sport) joined Ralliart in 2002, as a Race and Development Engineer. He was appointed Principal Rally Engineer in 2004and Chief Engineer from 2005 to 2007. Estrada explained to us that "the aerodynamic development was carried out in the wind tunnel of Lola (a renowned 50%-scale moving ground plane wind tunnel where wind speeds of up to 230 km/h can be reached). _We did not have any aero engineer in the team, so we took advantage of the vast expertise in aerodynamics of the Lola team, led by the talented Guillaume Cattelani (ex-Peugeot). We gave them our targets for the car and they did the design, based on their broad experience. They prepared a very detailed (1:3) scale model, with which they tested many different evolutions, especially rear wings and bonnets. They performed measurements with the car in frontal as well as sideways position until they reached the final design"._

## ⚖ Shifting the Balance

The new design included some original solutions never seen before back then on rally cars. The most visible one was the rear wing. As Estrada explains, "the rear wing gave us a lot of problems since the beginning. Initially, and due to marketing reasons, Mitsubishi wanted the rear wing to be located at the boot lid, as it was in the road car". And indeed, this is one of the first alternatives that were evaluated during the wind tunnel tests, as shown in the picture below.

<ImageWithCaption
 src="/assets/images/mitsubishi_WRC04_wind_tunnel1.jpg"
 alt="Mitsubishi Lancer WRC04 test model, Lola wind tunnel, 2003 - evaluation of a classic rear wing"
 layout="responsive"
 width="1600"
 height="1200"
/>

At first sight, it seemed logical to locate the rear wing at the boot lid, to take advantage of a cleaner airflow coming from the roof, thus increasing the efficiency in downforce generation. But there were other factors to consider, as Estrada details: _“The problem in a WRC car is not to generate downforce at the rear but at the front. Unless you create a disastrous design, the rear wing always creates a good amount of downforce. The real problem is to generate downforce at the car's front, and this is why we moved the rear wing forward, to move the center of pressure ahead, thus increasing downforce at the front. The result was a very balanced car"._

For this reason, the rear wing was moved forward, close to the rear windshield end. But, as Estrada details, it was not appreciated by everybody: _"although moving the wing ahead was allowed by regulations, nobody had tried it before on a sedan-type car like the Lancer. Nobody had understood that it could be located there, but it was completely legal. The FIA did not want us to use it in that position either, but the details of the regulations allowed to do it, and they had to accept it."_ The rear wing was finally located right behind the rear windshield, on the “upstream” part of the boot.

Then, due to regulations limiting the rear wing to just one wing, the lower wing had to blocked (as it had been done with the Evo V). For this reason, the lower wing was attached to the rear windshield. But this decision brought other consequences, as Estrada explains: _"Another problem was to open the boot. We had to spend a lot of money to design a system to open it, as the lower wing was in contact with the rear windshield"._ Both the upper wing and the lower plate included a <ExternalLink href="https://www.wrcwings.tech/2018/01/20/dan-gurney-footprint-in-2018-wrc-cars/">Gurney flap</ExternalLink> to improve their efficiency.

<ImageWithCaption
 src="/assets/images/mitsubishi_WRC04_2.jpg"
 alt="K.Sohlberg/K.Lindström, Mitsubishi Lancer WRC04, Rally Sweden 2004, retired - picture by Mitsubishi Motorsport Corp."
 layout="responsive"
 width="1295"
 height="866"
/>

Even though this was the final configuration to be implemented in the car, other rear wing improvements were evaluated in the wind tunnel. One was the addition of 4 vertical fins to improve the car stability and downforce generation while cornering. The picture below shows the test of this solution during a wind tunnel session, in a test with the moving ground on (see wheels rotating), the car sideways (to fully evaluate the efficiency of the fins) and with traces of yellow paint, probably used to visualize the flow distribution over the car.

<ImageWithCaption
 src="/assets/images/mitsubishi_WRC04_wind_tunnel2.jpg"
 alt="Mitsubishi Lancer WRC04 test model with vertical fins in the rear wing, Lola wind tunnel, 2003"
 layout="responsive"
 width="1600"
 height="1200"
/>

The arm located over the windshield was connected to a sensor to measure the load (downforce) generated by the airflow under different conditions. Notice also the fidelity of the scaled model in details like the bonnet design and the engine bay (to allow for a more accurate analysis of internal flows), or the roof scoop and the camera (which was, at the time, located next to the roof scoop on all cars).

## 🌬 Creating Breathing Space

Another area to which large efforts were devoted were the fenders. The designers suggested to go for very wide fenders (especially at the car's front), with the “downstream part” being open on both front and rear fenders. Using open fenders had a double advantage: first of all, improved evacuation of the air improves the flow rate through the wheel wells to improve brake cooling. Secondly, when more air is evacuated from the wheel wells, less air accumulates under the car and pressure (lift) is reduced. The result is moregrip.

The picture below show the design of the fender seen from the rear, both on the scaled wind tunnel model and on the real car. The results in the wind tunnel tests validated the design so that the team implemented these solutions into the car.

<ImageWithCaption
 src="/assets/images/mitsubishi_WRC04_wind_tunnel3.jpg"
 alt="Detail of the front fender in the wind tunnel scale model (left) and in Galli/D'Amore car in Rally Monte Carlo 2004"
 layout="responsive"
 width="1322"
 height="708"
/>

But, again, this decision created major problems for the team, as Estrada reveals: _"Leaving the rear of the fenders open did not make the FIA happy, and we had a lot of problems to homologate it. It was legal, but against the spirit of regulations, according to FIA. They tried to forbid them, based on these regulations, but they could not, as we had simply pushed the regulations to the limit without exceeding them. From 2005, FIA decided to ban open fenders, while now they are allowed again"._

<ImageWithCaption
 src="/assets/images/mitsubishi_WRC04_3.jpg"
 alt="G.Panizzi/H.Panizzi, Mitsubishi Lancer WRC04, Rally Cyprus 2004, retired - picture by Mitsubishi Motorsport Corp."
 layout="responsive"
 width="1252"
 height="834"
/>

## 😅 Keeping Things Cool

The third big area of improvement of the Lancer WRC04 was the front bumper, which had big benefits on the engine and front brakes cooling. _"The people at Lola did a great job on the aerodynamics of the front bumper, explains Estrada. The design of the lower part was entirely focused on improving engine cooling. That allowed us to significantly reduce the size of radiators. At the level of the front brakes, cooling was also very good, due to the two big ducts included in the front grille that fed fresh air to the brakes. It was so effective that we never had any cooling issue in the front brakes, in contrast to previous models which all featured brake cooling issues. The design was done with radiators, intercooler and brake cooling in mind"._ Cooling was also the object of multiple tests in the wind tunnel, evidenced by the great detail of the front bumper and bonnet in the scale model.

The final design of the front bumper included a very large central air inlet for radiator cooling, as well as inlets for the brake cooling (see the pipe inlet on both sides of the radiators in the picture below). Also, on both sides of the front bumper, a NACA duct shape (featuring the Magnetti Marelli sticker inside) was included to smoothen the flow of air to the car sides to reduce drag.

<ImageWithCaption
 src="/assets/images/mitsubishi_WRC04_4.jpg"
 alt="D.Solà/X.Amigó, Mitsubishi Lancer WRC04, Rally Catalunya 2004, 6th - picture by François Flamand/DPPI via Mitsubishi Motorsport Corp."
 layout="responsive"
 width="1383"
 height="927"
/>

Other distinctive features of the car were the roof scoop, designed with an ellipsoidal shape, and the bonnet air vents, located on both sides of the bonnet and protected with a small lip, in order to minimize the interaction of the hot air removed from the engine bay with the main, external flow.

## 🏁 Pusing the Limits

In conclusion, according to Estrada, _"Even though aero modifications were more restricted than in current cars (there was nothing we could do underneath the car, or at the doors), the car in 2004 was very balanced. With this car, we pushed aero to the limits, including solutions that had never been seen before, such as the open fenders, the rear wing location, front fenders design or the front bumper. A lot of effort was devoted to the front of the car. I believe that the Ford Focus 2003 had represented a step ahead in terms of aero, and the Lancer WRC04 was even one step further"._

<ImageWithCaption
 src="/assets/images/mitsubishi_WRC04_5.jpg"
 alt="K.Sohlberg/K.Lindström, Mitsubishi Lancer WRC04, Rally Finland 2004, retired - picture by François Flamand - Mitsubishi Motorsport Corp."
 layout="responsive"
 width="1384"
 height="886"
/>

## ☸ The Man Behind the Wheel

To learn more about the actual performance of the car, especially on the aero side, we contacted the 2004 Mitsubishi Official driver Kristian Sohlberg, who drove the car in five events that year, starting in Sweden.

A compressed development schedule was one of the first problems for the car, Sohlberg mentions: _"the car itself had a good chassis, but the team tried to do a miracle with the development work and testing starting so late, that it was never going to work, unfortunately. It would have been a good car with the right amount of testing and a proper development plan."_

<ImageWithCaption
 src="/assets/images/mitsubishi_WRC04_6.jpg"
 alt="K.Sohlberg/K.Lindström, Mitsubishi Lancer WRC04, Rally Sweden 2004, retired - picture by Mitsubishi Motorsport Corp."
 layout="responsive"
 width="1286"
 height="860"
/>

Over the first events of the season, the cars had to retire frequently due to reliability issues. This is common for a new car, but, in the case of the Lancer WRC04, solving them took much longer, as Sohlberg explains: _"We had so many issues with reliability through the whole year that aero was not the main point at the time"._

Reliability also affected the aero parts, as Estrada points out: _"In terms of aero, the car performed very well, but the problem was the durability of the aero parts, which we lost easily during the stages"._

<ImageWithCaption
 src="/assets/images/mitsubishi_WRC04_7.jpg"
 alt="K.Sohlberg/K.Lindström, Mitsubishi Lancer WRC04, Rally Cyprus 2004, retired - picture by François Baudin - Mitsubishi Motorsport Corp."
 layout="responsive"
 width="1616"
 height="1081"
/>

In spite of that, the hottest events showed some of the benefits of the aero design, as Sohlberg reports: _"The cooling was working fine even in harder conditions. In Cyprus we had a decent start of the rally but then a sumpguard issue made our life difficult as a quick release pin came loose and we could not attach the guard again. One of the stranger issues we had.... But cooling was working Ok"._

## 📰 Final Grades

The best results the car obtained in the 2004 season were two sixth positions by G.Panizzi/H.Panizzi in Rallye Monte Carlo and by D.Solà/X.Amigó in Rallye Catalunya.

The full story, including the performance of the car in the World Rally Championship, and the aero modifications implemented for 2005, can be found <ExternalLink href="https://www.wrcwings.tech/2020/07/21/mitsubishi-lancer-wrc04-aero-design-and-performance/">here</ExternalLink> as part of our series of articles devoted to the aerodynamics of the Mitsubishi Lancer Evo rally car model.

More information:

<ExternalLink href="https://www.wrcwings.tech/">WRC Wings</ExternalLink>
 

<ExternalLink href="https://airshaper.com/videos/rally-car-aerodynamics-side-slipping-through-the-air/video/hGK2wRVcALs">
 Video on Rally Car Aerodynamics
</ExternalLink>
 

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

Transforming Rally Car Aerodynamics - The Mitsubishi Lancer WRC04

## 🙋 About the Author

Koen Beyers is CEO of <ExternalLink href="https://www.voxdale.be/">Voxdale</ExternalLink>, a Belgian design & engineering company. Before founding the company, he had been working on the rear aerodynamics of Jaguar's Formula One car (back in 2001) . And with Voxdale, he worked on cool projects in amongst others Indycar, the European Nascar Series and now Formula E for Mahindra Racing.

## 🏎 Making the Difference

Formula E is a relatively young racing series featuring electric single-seater race cars. To keep the championship affordable, fair and competitive, the FIA has created a set of rules for the technical development. For example, the chassis and bodywork (designed and built by Dallara), brakes, tires, suspension and even the main battery are identical for all teams.

That means the teams need to look elsewhere to get the competitive edge, like drivetrain components. In the case of Voxdale, they looked at:

- Aerodynamics of the full car: although teams are not allowed to change the aerodynamics, understanding them is crucial for the setup of the car.
- The auxiliary 12V battery that powers the electronic systems for all the mission-critical systems in the car. Obviously, reliability was key.

## 📈 Aero Mapping

The setup of the car can make a tremendous difference in terms of lap times:
the ride height at the front & rear, for example, strongly influence the downforce & drag that are generated.

This setup also influences the aero balance - the split between downforce at the front & the rear.
The aero balance greatly affects the way the car handles, as it can induce / mitigate understeer and oversteer, how much traction is available, how stable the nose is at high speeds and so on.

As there is no time in the days leading up to the race or even during the race to analyse this, we created what is called an "aero map". This is a well-documented correlation between mechanical parameters (like the ride height front & rear) and aerodynamic performance properties. We used <ExternalLink href="https://www.plm.automation.siemens.com/global/en/products/simcenter/floefd-ptc-creo.html">Simcenter FloEFD for Creo</ExternalLink> to perform CFD (computational fluid dynamics) simulations to build this aeromap (<ExternalLink href="https://airshaper.com/blog/why-airshaper-complementing-ansys-starccm-powerflow-and-more">Read more</ExternalLink> about the complementarity of different CFD packages). Once we had it, we could use it to tweak the car's settings in no time to the specifics of each track.

<ImageWithCaption
 src="/assets/images/formula-e-public-model-pressure-map.jpg"
 alt="An AirShaper Illustration of the Pressure Map on a Formula E Race Car (based on a public model) - Real simulation images by Voxdale are confidential and cannot be shown"
 layout="responsive"
 width="835"
 height="684"
/>

## 🔋 Auxiliary Battery

Something entirely different was the 12V battery. This one powers all the mission-critical electronics systems on the car, so we couldn't take any chances.
We had clear goals for this part of the development:

- Safety: obviously, we couldn't take any chances in this regard. The battery had to be fireproof.
- Robustness: it had to withstand all the dynamic loads that come with a Formula E car going around the track
- Weight: it had to be extremely light to ensure proper balance & acceleration/deceleration of the car
- Cooling: batteries dissipate energy at high performance, so it needed to be cooled properly to avoid malfunction

This posed a number of engineering conflicts. For example, making the casing thicker made it stronger, but this also reduced the cooling performance (as the thermal resistance was increased as well). And with insufficient cooling, we would risk thermal runaway of the battery (battery heats up, which reduces electrical resistance, which means more current, which generates more heat).

So here too, we applied a lot of simulations to learn & fail digitally when testing dozens and dozens of different concepts. This approach allowed us to deliver a reliable solution in the end.

<ImageWithCaption
 src="/assets/images/formula-e-battery.jpg"
 alt="The Auxiliary Battery Casing of the Mahindra Formula E Race Car - Image credit: Mahindra Racing & Voxdale"
 layout="responsive"
 width="2560"
 height="1262"
/>

## 💡 Conclusion

Many aspects of the Formula E cars have been frozen by the FIA and for good reason. It all starts with a good understanding of the car, which in our case meant building a detailed Aero Map. And on the mechanical front, there is plenty of room left for proper engineering to make the difference when it comes to the drivetrain for example. This multi-disciplinary engineering challenge has been a real pleasure for the entire team :)

Interesting links:

<ExternalLink href="https://www.voxdale.be">Voxdale</ExternalLink>
 

<ExternalLink href="https://www.mahindraracing.com/">
 Mahindra Racing
</ExternalLink>
 

<ExternalLink href="https://airshaper.com/videos/race-car-aerodynamics-3-aero-mapping/video/u-GyTRblNmc">
 Video: What is Aero Mapping
</ExternalLink>
 

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

Formula E - Aero Mapping & Battery Tech

## 📢 Introduction

For this blog, we've had the pleasure of interviewing Per Lundstam, High Performance Manager at Red Bull. The combination of his background as an athlete and remarkable interest in sports technology have put him in a very interesting role!

<ImageWithCaption
 src="/assets/images/profile-per-lundstam-youtube.jpg"
 alt="Per Lundstam - Red Bull High Performance Manager - Source: 'Know Your Muscles' YouTube channel"
 layout="responsive"
 width="1581"
 height="616"
/>

## 🎿 From Athlete to Red Bull High Performance Manager

**Tell us something about you background and how you got into this industry?**
Absolutely, my background in the world of sports comes from when I was an athlete, which is where I started my career. This has been the precursor to my hole trajectory. Already as an athlete, I was very interested in what happens behind the scenes of high-level sports, specifically with skiing; what are its characteristics, understanding the underlying forces and all the different aspects, the biology of the sport, what effects does it have on your physiology, essentially the physics behind it all. From a young age I was inclined towards this side of sports, many athletes who are very talented in the sport certainly know what they do but, maybe they don’t have that interest towards a more scientific understanding of what happens. It might be because they simply don’t want to go along that path of understanding the science to a higher degree, they just simply execute the sport, indeed at a very high level.

I had a lot of that interest in understanding more about it, which drove me to go into coaching. I have coached for the Swedish national skiing team for quite a while back in the 90’s, my role being that of a coach in charge of all the physical aspects of the athletes. This led me, in 1994 to join the US skiing team, on the coaching side and thus stay there a long time before I was able to dig in a bit more and eventually join the sport-science team as a bridge between the athletes and the sport-science department.

**How rapid or challenging was the transition from being an athlete to coaching and working on the science behind the sport?**
It was a rapid, consecutive process for me. At that time when I was an athlete, I already did a lot of the training and programming for athletes, so that was like a natural path for me to step in to and take that direction.

## ⛷ Aerodynamics in Alpine Skiing

**Your holistic approach to the sport must have given you a privileged vision. Over the years has there been a change in attitude towards testing and aerodynamics from the athlete’s side?**
I think it is very sport-specific in how athletes look at their supportive work. You have technical disciplines such as alpine skiing or all the motorsports etc. where it has been understood that aerodynamics are essential to invest in and has a big effect on the outcome and results.

<ImageWithCaption
 src="/assets/images/lindsey-vonn-aerodynamics.jpg"
 alt="Aerodynamic Simulations on Lindsey Vonn"
 layout="responsive"
 width="1510"
 height="773"
/>

In alpine skiing you can definitely see that the culture has become more aware of the importance of aerodynamics in sports. I feel this has emerged from many of the faces of the sport. When I first started, it wasn’t as critical or relevant at the time, largely since there were so many other developments and holes to focus on that this was left aside. But as the sport has got more sophisticated, there is a true need to understand the aerodynamics behind it, and it currently is on everyone’s radar to develop. This comes along with the fact that more resources have been made available and come along to try and improve those few milliseconds that really make the difference in such high-end competitive sports.

**As a general idea, do ski teams outsource their aerodynamics research and development or do they invest in professionals and expertise to solve things in-house?**
That is a very nice question, for sure it is sometimes outsourced. Mainly experts and groups which are producing the materials and in charge of other areas of research, are the ones who determine what materials and shapes should be involved in and manage the aerodynamic research. I have seen that this development often must be so driven from the core team and treated from the beginning as something being intrinsically linked with other areas of study. Sometimes we have seen that we don’t have coaches or a direct sport-science connection bridging the athletes with the manufactures, in such cases it is very hard to create a product that has a true impact. Therefore, we are working hard to lessen the distance between the community and the groups who actually produce the materials, it is clear that the turnover of the product must emerge in harmony to really validate the effect it has. Projects in the past have been separated and fragmented, always resulting in making progress into something which is not very useful. Therefore, what you mention is an interesting dynamic in our world, we work as a team and face the problem from a holistic approach.

## 🏊 Hydrodynamics of Diving

**Making a move into a different topic, I am aware you have researched into the hydrodynamics of diving, please tell us about this project and why it arose?**
This project came directly from an athlete, like many other projects here at Red Bull, it was a cliff-diver who was in one of our programmes. To put you into context, these people jump from heights of about 27 meters, as you may imagine the impact and strain on the body is huge. Their velocities reaching 85 or 87 Km/hour when they hit the surface. After working some time with this athlete, we focused on the physical side and notices he was being injured in specific areas; adductors and shoulders.

We started talking about it and he told us that most of his competitors were also having these issues as a result of the high impacts. Their main problem was keeping their feet together and their shoulders perfectly aligned as they entered the water. We realised that it was interesting to see if we could come up with some equipment to assist them to keep their feet together whilst not restricting movement in the air. So that is where this project was born. We tried to figure out how to enter the surface without getting this jerking movement on the legs, which were the main cause of the injuries.

The first phase of the project was essentially recognising the problems and trying to give physical meaning to these issues, focusing on the entry point and changes in velocity. On a second phase we focused on how the body penetrated through the water and modelling the interaction of gas and air fluids and the consequence of formation of air cavities.

<ImageWithCaption
 src="/assets/images/red-bull-diving-analysis.jpg"
 alt="Red Bull - Experimental Setup to Analyse Forces on divers - source: the hydrodynamics of diving"
 layout="responsive"
 width="1297"
 height="681"
/>

## 🌬 Aerodynamics at Red Bull High Performance

**On your programmes, how dos aerodynamic testing come into play? Do you jump in from the start or develop this in parallel with all the other areas of research?**
It is very important to understand the aerodynamics versus the structural setup, like geometries and so on. We try to see how the athlete may still produce more power. It is always an interesting dynamic between the ability for the athlete to efficiently produce power and the aerodynamic and structural benefits we can obtain.

This happens in all sports but specially in cycling, a given position (which may indeed be very aerodynamic), can compromise athlete performance and thus not yield good results. We have had athletes that just by how their body is structured we may already be in a very nice aerodynamic position and still produce power, thus leading to great results. In the end it comes down to their body and how they can position themselves to produce this power, so it is very interesting to see that some athletes are fortunate enough to do that. In any case, most of our work was been directly tailored to the aerodynamics and testing on wind tunnels. For sure we have work on the road to look at, like how power profiles affect the changes in the position of the athlete.

**In terms of the research you do, are you limited to the number of simulations or testing you may do, or do you have complete freedom?**
From all the different federations and international committees, we do have strong regulations in terms of the material being used. As for the testing part, we are very much free, hence we try hard to push our understanding further by doing testing within those regulations.

## 🕐 Future Developments in Aerodynamics

**Coming back to the world of skiing, what are the future areas of focus from the aerodynamics side?**
The suit development is probably one of the larger pieces in ski racing where many of the teams and science groups are putting a lot of resources into, trying to break the wind and have materials that don’t let air through. From the ski side, the suits must let though a certain amount of air to fit into regulation norms, coming into game the scenes to visualise the flow and study how to reduce drag. Helmets are something on the eye of development from the least 15 years, even minute things like how goggles fit into the helmets may improve the drag.

<ImageWithCaption
 src="/assets/images/lindsey-vonn-tucked-position.jpg"
 alt="Aerodynamic Analysis of Lindsey Vonn in Tucked Position"
 layout="responsive"
 width="2805"
 height="1897"
/>

**Just out of interest, how many people are working on each athlete?**
It varies, but in most of our projects, as we spoke earlier, we outsource some of the work. From our performance team, we have had companies that come in with 3 or 4 main staff that drive the project and work together with us. Obviously, they may also have external teams that work for them aside, but I would say it is 3 to 4 people that usually come in and help us from our side. So, in general up to 7 or 10 people are working in the larger projects which have more resources.

## 💡 Conclusion

**Please tell us anything else you wish to talk about**
To sum up, aerodynamic research is a very interesting space and technology is something that is growing all the time in sports. We often see that we, as humans, have physiological limitations, so in the leading sports you start to look at other options and dimensions to go faster or achieve more. In technical sports, we have come a long way by developing and digging in aerodynamic research, putting resources into the technology to achieve a cohesive understanding of all the areas of focus. Undoubtably, there is going to be more and more focus on this side of sports, and awareness will be raised further in this space.

Interesting links:

<ExternalLink href="https://airshaper.com/cases/sports-aerodynamics-high-speed-skiing">
 Speed Skiing at 250 km/h
</ExternalLink>
 

<ExternalLink href="https://airshaper.com/cases/winning-the-red-bull-air-race">
 Winning the Red Bull Air Race
</ExternalLink>
 

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

Interview with Red Bull High Performance - Aerodynamics in Sports

## 📢Introduction

The world continuously changes, but the past months have been dramatically different.
The new Coronavirus COVID-19 has, most importantly, cost many lives and created a lot of stress in many families.

It has also shocked economies around the world.
Lockdowns have forced factories to close and people to work remotely, if at all.

So where does all this leave people working on aerodynamics?

## ❔Market demand

If you would have to list the top 10 global sectors that have been hit hardest by COVID-19, the automotive & aviation industry would both be in it or even take the podium. With hardly anyone buying a car when locked in their home and with continental & intercontinental flights reduced to almost none, you can imagine the challenges they face.

The racing segment had been hit particularly hard, with all races cancelled.
But even now that Formula One has restarted, it's not the same without an audience (in terms of entertainment but also in terms of income!).

So where do you put aerodynamics on the priority list in such scenarios?
Will you cut all non-necessary spending and do just what is needed to survive, risking long-term competitiveness?
Or will you take a leap of faith and keep investing in innovation, risking cash problems if the economy does not recover quickly enough?
Perhaps there is a middle ground.

## ☝Are Aerodynamics Essential?

### Aero-centered products

There is little use for planes or drones that don't fly.
So ignoring aerodynamics when it's at the core of your product is not an option.
That's an easy choice.

But in reality, it is a lot more complex:
if you're in racing, for example, will you maybe spend 30% less time on aerodynamics?
The car will still go around the track, but perhaps just 0.1 seconds slower per lap.
And that plane might still fly, but just 2% less efficient. Or less safe...

Most of these consequences are manageable in the short term.
But if your competitor chose the other route, to double-down on development, you'll be losing ground in the mid-to-long term.

### Aero-related products

For products where aerodynamics are not at the core, the story is different.
If you're designing a bycicle helmet for amateur use, ignoring the aerodynamics might not be such a big deal.
But then again, in such commodity markets, aerodynamics is one of the few remaining aspects to create differentiation for your product.
Not taking aerodynamics into account might make your product look more average, less special.

## 🌬 Option 1 - the Wind Tunnel

<ImageWithCaption
 src="/assets/images/windtunnelcentre.jpg"
 alt="One of the wind tunnels of Deutsche WindGard"
 layout="responsive"
 width="1275"
 height="337"
/>

It's no secret that despite our simulation platform we have a love affair with wind tunnels.
They are a fantastic tool to get fast, real-life data.

But the track to get to that data can be lengthy and expensive:

- Make your 3D design
- Build & construct a prototype
- Build a test-plan (what to measure, at what angle, ...)
- Instrument the prototype
- Move the prototype & the team to the wind tunnel
- Run the tests
- Post-process the data

In this scenario, you could reduce the team size present at the wind tunnel test.
Or double-down on rapid prototyping techniques to reduce throughput time & cost of the prototype.
Or perhaps dig-up some of your old prototypes and tweak those, to learn more about new concepts you are creating.
Or maybe you could even follow the test remotely if tasks are described properly to the wind tunnel team?

On the strategic side, there may be opportunities too:
wind tunnels are known to be booked for months in advance, having you queue for a slot.
Some may still have their first free spot only in 2021, but others seem to be having open slots.
This could be your time to get ahead of your industry competitors, or perhaps the situation can have an impact on the cost of using a wind tunnel.

Just ask <ExternalLink href="https://airshaper.com/partners/engineering"><a>our partner wind tunnel institutes</a></ExternalLink> what is possible!

## 🏎Option 2 - Track Testing

<ImageWithCaption
 src="/assets/images/tracktesting.jpg"
 alt="A Formula One car on the track with sensors mounted"
 layout="responsive"
 width="1000"
 height="667"
/>

If you're in the racing business, track testing is key:
lap times & rider feedback are the final judgement of your development work as a team.

But track testing has its limitations - you need a moving laboratory!
That means equipping your motorbike or racecar with sensors and data logging/transmitting capabilities.

Here, too, you may get creative:
with empty race tracks, your test slot just became available.
Or perhaps you could rent the equipment instead of buying it.
A variable cost per test might be easier to digest for the finance department compared to a big investment.

## ⌨Option 3 - Simulation

<ImageWithCaption
 src="/assets/images/simulation-lamborghini.jpg"
 alt="A Formula One car on the track with sensors mounted"
 layout="responsive"
 width="627"
 height="370"
/>

You might get hit in the face (if you're lucky) by the company's budget controller if you ask for a 50.000\$ CFD (computational fluid dynamics) license these days. As an engineer, it can be extremely frustrating to sit around & wait for a license to become available.
I remember the first thing we would do when arriving at the office (when I was designing gearboxes 12 years ago) was to open up Inventor (the CAD package we used back then). Why? Because then you were sure you had a license to continue work for the rest of the day.
But you'll still have to pay your engineers, whether they have a license available or not.
So cutting back on licenses is not as trivial as it may seem.

So, then, what's the alternative?
Well, over the past years we've seen many software providers implement cloud-versions of their software.
Sometimes they work with tokens, sometimes it's a lease, ...
Whatever the flavour is, the key point is that you can dynamically tweak the software needs to your team size & project phase.

- You don't need to run simulations this month? Perfect, then you don't need to pay.
- You need to run 50 simulations next month? Perfect as well, the scalable cloud is ready for you.
 An added bonus is that you don't need to invest in hardware to run all those simulations!

But even if you're not an engineer, this approach can pay off rapidly:
pay-per-use platforms allow you to select exactly the app you need, whether that is a thermal, mechanical or fluid simulation.

Or you can choose an app tailored to your skillset:
if, for example, you don't have an engineering or aerodynamics background and you still want accurate & fast aerodynamics results,
you can opt for a platform like <ExternalLink href="https://airshaper.com/#workflow">AirShaper</ExternalLink> that has the whole process automated.

## 💲OPEX replaces CAPEX

<ImageWithCaption
 src="/assets/images/opex-vs-capex.jpg"
 alt="The difference between CAPEX-based and OPEX-based approaches"
 layout="responsive"
 width="1204"
 height="643"
/>

In general, it's difficult for companies to invest in the current economic climate.
The return on investment is very uncertain and unless you're Apple, you probably don't have the cash to take that leap of faith.

So that favours options where you pay per use:

- Wind tunnels with flexible booking systems, remote test-it-for-you services, ...
- Tracks which offer measuring equipment for rent, track-side assistance per hour and perhaps even test-drivers on-demand?
 (I'll get shot for that last suggestion :) )
- Software solutions with a pay-per-use model, without any initial or monthly fee

In more general terms:
OPEX (Operating Expenditures, which vary "per iteration") could be more interesting than CAPEX (Capital Expenditures) in these times.

## 💡Conclusion

The conclusion of this article goes beyond aerodynamics:
not innovating will save you some cash in the short term but will cost you in terms of performance & market position in the long term.

So how can you still innovate in this uncertain climate?
Look for solutions that favour OPEX over CAPEX and pay as you go to limit the risk!

The art of bootstrapping for startups could soon become common practice for corporates :)

More information:

<ExternalLink href="https://airshaper.com/#workflow">
 How AirShaper Works
</ExternalLink>
 

<ExternalLink href="https://airshaper.com/pricing">
 AirShaper Pay-per-Use Pricing
</ExternalLink>
 

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

Aerodynamic Innovation in Times of COVID-19 - How to stay healthy in the long term without burning your cash

## 📢Introduction

When I made the transition from university to industry, I was truly shocked:

no longer did I have time to solve problems purely from a technical point of view with fairly large amounts of time to do so.
Things had to be delivered within someone else's planning and very often that lead to good but non-perfect solutions.
After being trained for 5 years to pursue mechanical perfection, I had to deliver 5 solutions which were "good enough" instead of 1 perfect solution.

I felt dirty :)

## ⌚A Time and Place for Everything

Truth is though, if you zoom out, this makes sense in many cases:
rapidly creating 5 different designs and testing them (physically or digitally) will create a lot more insight than perfecting one.
You're still chasing that technical solution, just like at university, but the path that leads to it is very different.

One doesn't exclude the other:
over time I have come to appreciate that there is a time and place for everything.
If you're working on fundamental research, you need to work extremely in-depth to make sure the foundations are correct - after all, real-world applications & products will be built on top of your research at some point.
But if you're working on those real-world applications & products, you'll be faced with rapidly changing market demands, customer desires, product release cycles and much more. So taking the time to perfect things might leave you with a perfect yet outdated product by the time you launch.

It's the undeniable, perverse nature of our economic system :)

## ☝My First Encounter with Aerodynamics & CFD

My first encounter with aerodynamics was a gut-feeling based sports car I designed in my free time, featuring internal & external air channels to generate lateral aerodynamic forces. No tools involved, just love for physics. Without tools, I could only go a certain length and although the concept got patented and I got to talk to Ferrari (who referenced to my patent in theirs) & Pagani (I got to meet them at their office!), the project died.

<ImageWithCaption
 src="/assets/images/aquilo-patent.jpg"
 alt="Patented Concept for Lateral Aerodynamic Force Generation"
 layout="responsive"
 width="621"
 height="340"
/>

Later, when I started running actual CFD (computational fluid dynamics) simulations and wind tunnel tests when working at Belgian engineering agency Voxdale, this fed (and corrected) my internal physics engine. Feeling real wind, seeing turbulence on your computer screen, putting tufts on a car, ... it all helps.

Back then, we worked with FloEFD by Mentor Graphics. It's based on a modified k-epsilon RANS solver - not top of the line but not too basic either and very user friendly. Exactly what we needed in terms of accuracy versus cost versus throughput time for all the race car, drone and building projects we were doing.

## ⛓50 Shades of CFD

So why, then, was FloEFD bought by Siemens? They already had StarCCM+, a top of the line software package widely used in automotive for example. Well, each software package has its unique trade-off: StarCCM+ has all the tricks & options you need to achieve that ultimate accuracy, but you'll see some black snow before you get to the good stuff & produce reliable results. FloEFD, on the other hand, is much more accessible, and you'll still be able to work with it if you haven't used it for a year and want to jump back in.

<ImageWithCaption
 src="/assets/images/shades-of-cfd.jpg"
 alt="Many CFD software solutions exist in the market"
 layout="responsive"
 width="1619"
 height="431"
/>

Siemens is not the only one offering a range of CFD software packages though. Dassault Systèmes, who also offer Solidworks, merged Exa Powerflow, another highly-reputed aerodynamic simulation software package, into their offering. Whether it's StarCCM+, Powerflow, Ansys Fluent or Altair Hyperworks, they each have their own blend of user features, cost, ease of use and so on - all of them aimed at skilled CFD engineers. Choosing a package comes down to your budget, obviously, but also your skillset, timeline and most of all application.

## ⚡Common Challenges

In the case of AirShaper, that application is external aerodynamics. The field of many fascinating product developments such as cars, trucks, buses, planes, drones, sports equipment and even athletes! As you can imagine, the aerodynamic skills of the users performing simulations vary tremendously, from "never touched CFD software before" to "I eat CFD for breakfast" (CFD not meaning "crunchy fried doughnut" if you were wondering 😎)

Whatever the background or skill of the user, they all need to cope with similar challenges:

- **Getting the 3D model**:
 3D files are often not available for a racecar (manufacturers don't exactly hand those out), let alone a 3D model of an athlete!
- **Fixing the 3D model**:
 Very often, depending on the software, a 3D geometry needs to be made watertight (meaning all gaps & holes need to be closed). A tedious, time-consuming task.
- **Setup complexity**:
 Setting up a simulation usually requires a sound degree of expertise, as there are literally dozens of parameters that can influence the simulation stability and results
- **Meshing**:
 Meshing is the key to a proper CFD simulation (although some interesting meshless solutions are becoming more popular).
 It's one thing to get a proper initial mesh, it's another thing to refine it properly during the simulation (something called adaptive mesh refinement)
- **Hardware**:
 Unless your name is Adrian Newey, you'll need a computer to solve your aerodynamics problem.
 With ever-rising demands on accuracy, the hardware needed is often comprised of tens or hundreds of cores and Gigabytes or even Terrabytes of RAM memory.
- **Post-processing**:
 Once a simulation is done, you'll need to process the results into data and visuals that are easy to understand.
 Only then can you start to understand the problem after which you can redesign & re-calculate new design options.

## 🔗General Purpose or Application Specific

If you're running all types of simulations on different applications (like a consultancy agency) you may favour a general-purpose CFD software package.
This will allow you to apply thermal simulations for one project, compressible flow for another, and so on.
If you're an expert, this is a really cool option, because you can control every single parameter:
You're an expert, you know what to do. You're in charge of 3D model fixing, meshing, solving, post-processing and so on.

Or, you can go for an application-specific CFD software package:
there are solutions tailored to aviation, supersonic flows, and - you guessed it - incompressible external aerodynamics, our playing field at AirShaper.
The cost of such packages is typically much lower as you don't have all the options. And setup us much easier, as unnecessary features are removed.

## ⏲The Right Time for the Right CFD Software

You could also consider combining software packages, especially in bigger firms:
as a designer, you can be working on initial concepts which are then, after months of work, sent to the engineers for review.
After fixing the 3D model (if you're the designer, you may spend some weeks on this), they'll run simulations and let you know what and where to change the design.

The good thing is that each person does what they are best at: the designers design and the engineers crunch numbers. The bad thing is that this creates isolation & underappreciation for each other's domain. The designers get annoyed when something needs to be changed because of the aerodynamics and the engineers complain that the designers keep suggesting unrealistic shapes. So giving the designers an easier-to-use version of that aerodynamics software solution could work miracles.

Also, this greatly reduces the development time:
using a fast & flexible simulation tool in the early stages of design quickly sets you off on the right track. That avoids months of rework compared to when you only run the first simulation after months of work, only to find out there are serious issues.

## ❔Why AirShaper

So why, then, did we start AirShaper?
Well, we like StarCCM+, Ansys Fluent, Exa Powerflow, Altair Hyperworks and so on. But just like I was struggling myself to get my hands on some initial feedback of the car I was designing 12 years ago, so are others.

An easy to use, online platform that:

- works with non-watertight 3D models (including 3D scan files)
- takes automated control of all simulation parameters
- automatically creates & adaptively refines the mesh
- drops a simulation report in your mailbox when it's done
- costs less for a one-year subscription than the yearly maintenance cost of a general-purpose CFD software

really makes the complex domain of aerodynamics accessible to a much broader audience.

And, interestingly enough, we also have a good deal of CFD experts using AirShaper as well:
yes, they still love to control everything, but quickly firing 10 comparative simulations in the cloud at the very early stages leaves their hands free to work on more customized simulations for other projects.

## 💡Conclusion

All of the software packages discussed above have their right of being:
when extreme accuracy levels are required, you simply need a CFD expert to control the buttons and a software package with... enough buttons.
But there is a whole parallel universe where fast and accurate simulations greatly help to speed up design work, increase insight and even enable companies without previous CFD simulation expertise to inject some aero-magic into their products.

That's why we run AirShaper.
And we're proud to complement the big boys like StarCCM+, Powerflow and Fluent.

More information:

<ExternalLink href="https://airshaper.com/#workflow">
 How AirShaper Works
</ExternalLink>
 

<ExternalLink href="gttps://www.airshaper.com/pricing">
 AirShaper Pricing
</ExternalLink>
 

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

Why AirShaper - Complementing the Big Boys - Ansys Fluent, Siemens StarCCM+, Exa PowerFlow and others

## About the Author

Dr. Rainer Buffo is the CEO of <ExternalLink href="https://www.betterflow.com">"Betterflow GmbH"</ExternalLink>, a company specialized in optimizing the aerodynamics of trucks and trailers to reduce fuel / battery energy consumption. Next to their existing range of fuel-cutting add-ons for trucks, they also work on & lobby for more drastic changes to the shape of future trucks - Enjoy the blog post!

## About the Tesla Semi

Heavy-duty trucking is a conservative business: every minute and every dollar/euro counts and margins are low. There's definitely interest to reduce fuel or battery energy consumption, as this directly impacts the profitability of trucking companies. Our starting point today is the existing truck-trailer layout which is optimized around businesses, daily operations and regulations but suffers from an unattended aerodynamic health condition. But with the right treatment using effective add-ons and adjustments there is room for innovation and efficiency leaps. And there’s so much more to achieve!

So we were thrilled to see Tesla shocking the industry by presenting an extremely streamlined truck. It opened up the minds of people to rethink what could be possible and a drag coefficient of 0.35 is an impressive achievement.

<ImageWithCaption
 src="/assets/images/tesla-semi-drag.jpg"
 alt="The announcement of the 0.35 drag coefficient of the Tesla Semi"
 layout="responsive"
 width="2816"
 height="982"
/>

One thing Tesla didn't really touch was the trailer (which makes sense, as they focused on electrifying the truck). Yes, the truck was optimized to deliver clean airflow to the trailer it is pulling, but from there on, it is back to usual business with a boxy trailer.

## Making the Truck & Trailer play together

We work on optimizing existing trailers every day, as much as we can within the newest regulations: we add flaps at the rear to help close the wake, we optimize the top to better accept incoming air from the truck and we "clean up" the flow underneath the truck. And that's where it gets interesting.

<ImageWithCaption
 src="/assets/images/addons.gif"
 alt="Add-ons for the drag reduction of trucks"
 layout="responsive"
 width="1200"
 height="802"
/>

In parallel, we're designing the ultimate aero-truck to make a mark on the (road)map in terms of what is realistically possible for truck-trailer aerodynamics in the future. It's called the "2032 Future Truck". When you make the truck & trailer work together you can really go far beyond the 0.35 Cd value of the Tesla Semi!

## Bottoms up!

One key aspect of optimizing the airflow of a truck is to look at how the airflow moves underneath. The traditional train of thought (pun intended) is to shield the sides of the trailer to prevent flow from moving in and out from underneath the trailer / hitting the tires. That makes sense, as the truck has already pushed that air out of the way and the trailer can hide in this wake. But that means there is a "pocket of air" below the trailer being dragged along, virtually increasing the "frontal area" or "cross-section".

<ImageWithCaption
 src="/assets/images/pocket.jpg"
 alt="A Pocket of Air underneath the Trailer"
 layout="responsive"
 width="1326"
 height="523"
/>

In our Future 2032 truck, we have completely redesigned the truck to allow for air go dive underneath the cabin, between the wheels. This channel is then continued underneath the trailer, where the air can flow freely between the left & right wheels (which are shielded to reduce drag).

<ImageWithCaption
 src="/assets/images/air-channel.jpg"
 alt="A channel beneath the truck & trailer to allow airflow"
 layout="responsive"
 width="1078"
 height="523"
/>

Together with front & rear guiding vanes, we can create a high-speed flow all the way from the front of the truck to the rear of the trailer. Comparing to an indicative 3D model of the Tesla Semi, first CFD (computational fluid dynamics) estimates indicate that **the drag coefficient is almost 30% lower than the Tesla Semi**. Some might call this Black Magic! We think it's the next go-to treatment for the airflow around trucks.

<ImageWithCaption
 src="/assets/images/betterflow-concept.gif"
 alt="The Betterflow Future Truck 2032 Concept"
 layout="responsive"
 width="640"
 height="360"
/>

## From Concept to Reality

We realize this concept cannot be made within existing road transport standards & habits. And maybe it will not look exactly like this in 2032. But we are working hard on creating awareness on its potential in different sector groups and regulatory organizations to pave the way for the necessary changes. Betterflow wants to make a substantial difference in terms of fuel emissions and battery energy consumption!

More information:

<ExternalLink href="https://www.betterflow.com">
 Betterflow Website
</ExternalLink>
 

<ExternalLink href="https://airshaper.com/videos/cutting-truck-bus-emissions-the-vecto-airdrag-tool/video/s2QyP6n4Zxs">
 Cutting Truck & Bus Emissions - The Vecto Airdrag Tool
</ExternalLink>
 

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

Looking beyond the Tesla Semi - The Betterflow Future Truck 2032 Concept

## About the Author 📢

Vincent Keromnes works at <ExternalLink href="/partners/engineering/a2mac1">A2MAC1</ExternalLink>, a company specialized in benchmarking the performance of cars. Lots of cars. Vincent is in charge of what they call "Dynamic Benchmarking", covering Kinematic & Compliance testing, Energy Management Strategy, Battery Thermal management and so on. Recently, they added aerodynamics & aero acoustics to that list - the perfect timing for a blog article!

## Physical or Virtual Wind Tunnel? 🌬

We have several options to benchmark the aerodynamic performance of vehicles and we aim to get the best value out of each approach.

We analyze cars that are already available on the market. Running them through a physical wind tunnel test means you have the real shape (which can differ quite a lot from the digital mockup produced during development) in real wind conditions. But each wind tunnel has its own specific setup (attachment points, moving ground area, ...). This is ok when you're comparing the data with other vehicles tested in the same tunnel, but things get tricky when comparing with data from another tunnel or simulation data.

CFD (Computational Fluid Dynamics) simulations on the other hand can provide insights on digital models before the car is even built. Another advantage is the possibility to simulate real road conditions (without the limiations of a physical wind tunnel). But here too, comparability between different CFD methods is challenging, let alone the comparison to a wind tunnel test. The only solution for the latter is to include the full wind tunnel into the virtual CFD simulation.

In this blog, we'll compare the physical wind tunnel test with a CFD simulation applied on a high-quality exterior of the Tesla Model Y.

## Physical Wind Tunnel Setup ⚙

We took the Tesla Model Y to the <ExternalLink href="https://www.soufflerie2a.com/">S2A</ExternalLink> wind tunnel for a thorough airflow analysis. This tunnel has been used for many cars in the past and features a moving ground (although it is limited to the area between the wheels) and allows for the wheels to rotate.

<ImageWithCaption
 src="/assets/images/tesla-model-y-in-the-wind-tunnel.jpg"
 alt="The Tesla Model Y in the S2A Wind Tunnel"
 layout="responsive"
 width="1438"
 height="959"
/>

Using smoke the flow pattern of the wind around the car was made visible. And using special techniques, the total pressure in a plane just 100mm behind the car was measured, giving good insight into the structure of the wake behind the car.

## The Virtual Wind Tunnel Setup 💻

To run a CFD simulation we needed a 3D model. In this case, a highly detailed scan of the exterior was made and then modified to increase realism: gaps between body panels were kept as geometrical discontinuity but were closed to avoid "false airflow" and the underhood flow was blocked by adding planes behind the grill. As for the aircurtains (small channels at the sides of the front bumper that provide a "shielding" layer of air across the front wheels), the inlets & outlets were part of the scan, but the duct connecting them to improve the flow was not (allowing for some air to escape "inside the car").

<ImageWithCaption
 src="/assets/images/tesla-model-y-scan-images.jpg"
 alt="3D Scan of the Tesla Model Y"
 layout="responsive"
 width="1236"
 height="817"
/>

Once this was done, an AirShaper simulation was run. It also featured roating wheels and a moving floor (everywhere, not just between the wheels). The support arms used in for the wind tunnel test were not included.

<ImageWithCaption
 src="/assets/images/tesla-model-y-cfd.jpg"
 alt="CFD results for the Tesla Model Y"
 layout="responsive"
 width="1298"
 height="594"
/>

## Results 🖇

We can't publish the full AirShaper report and the full S2A report (as these are documents available for purchase at either company). What I can share is the following:

CdA: the AirShaper simulation predicts a CdA which is 5-6% higher than the wind tunnel result. This can have many reaons, but in part this is because of the missing aircurtain ducts in the 3D model (increasing drag in the virtual wind tunnel simulation) and the narrow moving floor (reducing drag in the physical wind tunnel test).

Pressure distribution: below you can see the pressure distribution in a cut plane taken at 100mm behind the car. The global shape is very comparable, confirming the complementary & correlation between both techniques, despite their differences in setup & execution. The largest differences are close to the ground, where the physical wind tunnel (narrow moving ground) and virtual wind tunnel (full moving ground) feature a different approach.

<ImageWithCaption
 src="/assets/images/tesla-model-y-total-pressure.jpg"
 alt="Cut plot of the total pressure 100mm behind the Tesla Model Y"
 layout="responsive"
 width="1928"
 height="649"
/>

## Cost 💲

Last but not least, I admit that the cost of doing a full vehicle scan and setting up a complete simulation manually yourself can cost as much as a physical wind tunnel test. By grouping all of these A2MAC1 scans & AirShaper simulations and offering the combined result to multiple users, the cost drops dramatically and understanding the aerodynamics of existing cars suddenly becomes much more accessible.

## Conclusion 💡

I will not enter into a debate discussing the difference between the two approaches - I've been trapped in this kind of discussion too many times during my career - it would never end 😏. The real value of vehicle performance analysis is not in the absolute values: benchmarking is about relative differences, with the goal of ranking the performance of different cars.

The most reliable approach is to use a robust protocol and a set of best practices applied in a systematic way, consistently using the same tools (whether they are physical or virtual).

<ExternalLink href="https://app.airshaper.com">
 Start your own simulation here
</ExternalLink>

Benchmarking the Tesla Model Y - Different Ways to Analyse the Aerodynamics

## Removing the pilot 🛩

As if developing their own four-seat passenger aircraft wasn't hard enough, <ExternalLink href="/partners/engineering/cfd-consultants">CFD Consultants GmbH</ExternalLink> are now working on an unmanned version of their baby.

They formed a network of aviation specialists to develop an innovative four-seat passenger aircraft called the TR230. After years of hard work, the prototype of the TR230 is about to successfully finish the flight test program. And already, they are working on their next move – they co-founded iViation GmbH to bring UF230 into the market: a freighter version to carry goods … without a pilot! The first certified autonomous cargo aircraft worldwide!

## Fast Conceptual Comparison 👁

To carry as much as possible, the cargo volume needed to increase to a minimum of 3m3. Making it wider reduces the usable wingspan and thus lowers maximum take-off weight, making it higher affects landing & take-off behaviour and sizing constraints, ... With a multi-variable problem like this, fast iterations on the global shape are crucial to gain insights & make crucial design choices.

<ImageWithCaption
 src="/assets/images/body-width.jpg"
 alt="AirShaper simulations performed on different body sizes"
 layout="responsive"
 width="1800"
 height="731"
/>

In a first phase, they used AirShaper to compare multiple versions in terms of aircraft drag for a given (required) lift performance of the plane. With minimal effort & in a very short time, they were able to conclude that the wide-body fuselage had some operational advantages apart from decent aerodynamic performance.

## Finetuning the Details ⚙

In a second phase, they went on to perform custom simulations including the propeller, cooling airflow, flap configurations and so on, all featuring high-end boundary layer resolution & advanced turbulence modelling aimed at fine-tuning the aerodynamics and obtaining flight loads for certification. They ended up with a flap design that provides high lift coefficients and leads to outstanding short field qualities of UF230.

<ImageWithCaption
 src="/assets/images/cfd-on-flaps.jpg"
 alt="Close-up of the flow through and around the flaps"
 layout="responsive"
 width="1837"
 height="890"
/>

## Conclusion 💡

In conclusion, using the right tools at the right time can really help to speed up the pace at which you gain insight. And that directly shortens the design cycle!

<ExternalLink href="https://app.airshaper.com">
 Start your own simulation here
</ExternalLink>

World's First Certified Autonomous Cargo Aircraft - How a group of passionate aviation specialists is developing the first autonomous cargo plane.

## Introduction

The top 3 question we receive from students are:

- How can I build a career in aerodynamics?
- Do you have an open position at AirShaper / know of another company with open positions?
- Can you support our Formula Student team?

In this blog we'll zoom in on the first & second question:
👣Which steps do you need to take to lang a job in the fascinating world of aerodynamics!

## Education 🎒

Yes, this is important: if you're applying for a job, your education matters. Most (mechanical) engineering bachelor or master tracks will include at least an introduction to fluid mechanics, as it's crucial to many engineering problems (damper design, hydrodynamics, HVAC - heating, ventilation and air conditioning, ...). Or, you can follow a master really dedicated to the field of fluid dynamics, often with a choice between experimental (real-life testing) and/or computational (computer simulations). Of course, the choice of the institute is important: some, like the TUDelft in the Netherlands, have a superb reputation and that will help you shine on your CV. Finishing such a master is of course fantastic, but still, you will not be entirely unique (unless you were the only student to follow that course, in which case you may want to question the course itself 😎).

<ImageWithCaption
 src="/assets/images/tudelft.jpg"
 alt="Courses on Aerodynamics at the TUDelft, Netherlands"
 layout="responsive"
 width="1577"
 height="668"
/>

There is something else which is, at least in my opinion, equally important:
self-study.
Companies will appreciate & sometimes even demand the skills & knowledge you gained through your studies, but they will in many cases look for something extra, something that sets you apart.
If you can talk at length about the go-kart you pimped aerodynamically in your backyard, or how you spent long evenings programming your own CFD (computational fluid dynamics) code, this can really set you apart.

## Exposure 🗣

You can have plenty of skills, but you'll have to make them known to the world. Applying for open positions is an obvious way of doing so. But you could also build a network, even before you graduate, in the aerodynamics scene: write a blog, write stoties on Linkedin, post aero stuff on Twitter, ... let the world know you have a burning passion for aerodynamics.

It's not a straight path to success, and it's difficult to gauge the "return on investment", but you may be surprised by how you can sometimes end up talking to interesting people. And don't let anything hold you back: even if the people you want to talk to are senior people at respectable companies, just give it a try: add them on Linkedin, send them that interesting paper you did on your go-kart.

<ImageWithCaption
 src="/assets/images/willem_toet.jpg"
 alt="Willem Toet - Sauber"
 layout="responsive"
 width="1044"
 height="687"
/>

Last but not least, don't underestimate the physical world:
Motorsport fairs for example (like the ones in Birmingham or Cologne) are a great place to find & meet very interesting people. I've had multiple encounters with Willem Toet, for example. He's a legend in terms of aerodynamics, has worked at Sauber for years, but is one of the most charming & accessible people in the entire racing scene. He & others like him often give interesting (free) talks at such events. After the talk? Just walk up there and tell an interesting story that sticks! As to date, there is no app that will replace the quality of a face-to-face meeting 😇

## Dedicated channels⚡

The first person ever to start working at AirShaper came to us via a job we had placed on <ExternalLink href="https://www.cfd-online.com/Jobs/">CFD Online</ExternalLink>, a specialist forum dedicated to computational fluid dynamics. In a similar way, but then dedicated to aerodynamics rather than CFD, we've created the <ExternalLink href="https://www.airshaper.com/jobs/landing">AirShaper Job Board</ExternalLink>. On this free & open platform, people can create a profile to be discovered and companies can post vacancies.

## Indirect paths 🏎

If you're dreaming of a job in Formula 1, don't over-focus on it.

First of all, being responsible for the aerodynamics of an entire car at a small company might be more rewarding than working on barge board number 3 on a Formula One car.

Second of all, an indirect path might actually be the more efficient & interesting one. Even if you start out working on drones, you may still end up at a race team later on. They might even value your expertise from a different sector.

Just stay open to interesting things that cross your path, instead of focusing solely on that ultimate goal. For all you know, you may discover another domain you find even more interesting!

## Perspective 📷

A cheesy one, but don't forget to live :)
Working on something you're passionate about is great, but please do balance work with other interesting things to do - it'll feed your creativy and keep you fresh!

## Conclusion 💡

Besides proper education, applying your passion to private projects and talking about it to people around you and people in aerodynamics scene can really make a difference. Go beyond the text books that others have read as well and play around, experiment and enjoy aerodynamics - by doing so, you'll come across interesting people & opportunities in life!

Building a Career in Aerodynamics - From learning CFD to wind tunnel testing to feeling the physics to landing a job

## About the Author

In this blog post, Laurent Bohez of Vault Engineering runs us through his personal dream to combine classic looks with cutting edge technology!

## Background

Cars designed in the 1960s lack many performance-increasing features. The way their chassis have been conveived for example, is completely different from today’s performance cars. And that’s not to mention aerodynamics – a field I didn’t realize was so crucial to performance before I started this project.

<ImageWithCaption
 src="/assets/images/ferrari_p4_rear_view.jpg"
 alt="Ferrari P4 Style Race Car"
 layout="responsive"
 width="1387"
 height="867"
/>

I’ve been working with old-timers my entire life, mainly improving mechanical parts – changing these really had a tangile impact on the driving qualities of the car. But this project takes place at a different level with much bigger expectations. Building a high performance racing car is art, every car fanatic knows that. The real art is to make the different physics work together - matching the aerodynamic balance to the weight balance for example.

<ImageWithCaption
 src="/assets/images/modern_lemans_race_cars.jpg"
 alt="Modern LeMans Race Cars"
 layout="responsive"
 width="1387"
 height="924"
/>

## Matching virtual and real world

The first step was to analyze the airflow on the original car. Very basic, no rotating wheels or different heights, just pure form. This is crucial to know where to start in terms of improvements. A small adjustment can make a big difference, but I always say: first we have to understand what is happening before we can turn it into true knowledge.
After the calculations with airshaper it was very clear what we were dealing with: huge amounts of lift on the nose and a negligible amount of downforce on the tail. And if you look at old images from the 24H of Le Mans you can indeed see how the nose lifts itself at high speeds. It must have been really terrifying to drive this machine!
I am a huge supporter of simulation software but I also like to compare results with reality. For example, I spoke to a person who raced the real cars for years as well as replica’s these days together with David Piper. I was so excited that he told me the simulation values depicting lift on the nose corresponded perfectly with what he had felt in these cars. A huge step forward! Now the real work can begin: bringing harmony and balance to these iconic cars.

<ImageWithCaption
 src="/assets/images/david_piper_ferrari_p4.jpg"
 alt="David Piper in his Ferrari P4"
 layout="responsive"
 width="564"
 height="375"
/>

## Underfloor Aerodynamics

Like many, I’m a big fan of Adrian Newey. Seeing his latest creation, the Aston Martin Valkyrie, I came up with some great ideas together with airshaper. What classic cars really lack is proper underfloor aerodynamics. And as this doesn’t impact the classic look of the bodywork on top, we can really increase downforce without visual compromise. Support arms are now placed much higher to create room underneath special aerodynamics wizardry. We might even succeed at getting the front down force we need without using a front splitter!

<ImageWithCaption
 src="/assets/images/underfloor_aerodynamics.jpg"
 alt="Underfloor aerodynamics"
 layout="responsive"
 width="1228"
 height="483"
/>

For more information, visit <ExternalLink href="https://www.vault.engineering/project-p4/">"Prototyping the Prototype"</ExternalLink> 

<ExternalLink href="https://app.airshaper.com">
 Start your own simulation here
</ExternalLink>

High-Tech Classic Motorsport - Building High-Performance Race Cars with an Iconic Shape


## Passion for Aerodynamics

Yes, running a startup is hard work. Very hard work. But we started this journey straight from the heart - based on our Passion for Aerodynamics. Through this blog, we want to (re)connect with that fire, by discussing science beyond the numbers: why aerodynamics are cool, how this field helps to shape (part of) our world and who the people are behind some of the world's coolest cars, drones, buildings and more!

## Up close & personal

No matter how fast or efficient, numbers and science only come to life when they affect your experience and emotions. In our very personal case, we started [designing a sports car](/cases/aquilo) about 12 years ago - AirShaper didn't even exist. Passion drove us and by chance, it led to AirShaper. This blog will cover the drive behind projects - which we've already felt when interviewing others, like Lowie Vermeersch (the design genius behind the [Ferrari 458](/videos/lowie-vermeersch-1-ferrari-458-to-lightyear-one/video/o4Yv5hynV1Q), [Lightyear One](/videos/lowie-vermeersch-2-the-lightyear-one-solar-car/video/TKHjyC_L0OM) and [Dallara Stradale](/videos/lowie-vermeersch-talks-4-the-dallara-stradale/video/c7NyvCluYVc)). But we won't be talking just about cars - we'll bring you the stories behind drones, ships and more!

## Open Community

This blog will be open to guest writers - customers and non-customers - talking about their love affair with aerodynamics. So if you feel you have an interesting story to share about a project or product where the airflow has made a difference, or an experience that gave you goose bumps - [let us know](mailto:info@airshaper.com)!

Enjoy!!


AirShaper BlogPassion for aerodynamics

The Case of the Mercedes EQC Drag Coefficient

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