## 🙋 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."
 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."
 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."
 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)."
 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/XntO27S5Urc">
 How to Interpret CFD Results
</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."
 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"
 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."
 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"
 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"
 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."
 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."
 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."
 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."
 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."
 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/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"
 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"
 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/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"
 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"
 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"
 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"
 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"
 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">our partner wind tunnel institutes</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"
 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"
 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"
 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"
 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"
 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"
 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"
 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"
 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"
 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"
 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/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"
 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"
 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"
 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"
 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).

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 Start your own simulation here
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AirShaper BlogPassion for aerodynamics

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

Benjamin Rembold

Transforming Rally Car Aerodynamics - The Mitsubishi Lancer WRC04

Lluis Vazquez Vilamajo

Formula E - Aero Mapping & Battery Tech

Koen Beyers

Interview with Red Bull High Performance - Aerodynamics in Sports

Nicolas Berberoff Naval

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

Wouter Remmerie

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

Wouter Remmerie

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

Dr. Rainer Buffo

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

Vincent Keromnes

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