## 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"
 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"
 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"
 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"
 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"
 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/DqlDpUFcScc">
 From 3D scan to Aerodynamic Simulation of a cyclist
</ExternalLink>
 

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

<ExternalLink href="https://airshaper.com/videos/cfd-results-how-to-interpret-an-aerodynamic-analysis/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"
 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"
 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"
 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"
 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"
 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/simulations/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"
 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"
 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"
 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"
 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"
 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/u-GyTRblNmc">
 Aero mapping for race cars
</ExternalLink>
 

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

<ExternalLink href="https://airshaper.com/videos/cfd-results-how-to-interpret-an-aerodynamic-analysis/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"
 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"
 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."
 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."
 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."
 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."
 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"
 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/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/AdGuENBuZ-Y">
 America's Cup Aerodynamics - Interview with AIRBUS - Part 1
</ExternalLink>
 

<ExternalLink href="https://app.airshaper.com/simulations/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."
 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/simulations/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/simulations/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/simulations/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.

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/simulations/new?accuracy=regular">
 Run your own Simulation
</ExternalLink>

AirShaper BlogPassion for aerodynamics

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Transforming Rally Car Aerodynamics - The Mitsubishi Lancer WRC04

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Formula E - Aero Mapping & Battery Tech

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Interview with Red Bull High Performance - Aerodynamics in Sports

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