Student Formula Aerodynamics: Inside Revolve NTNU

Ebbe: I am here with Isaac and Peter from the Revolve team of 2023. So we will talk about the Revolve organization, student formula, the arrow package, and then talk about a component called the shark fin on the car. So warm welcome, guys, and please help me introduce yourselves. So who are you, what do you study, and why did you join Revolve?

Isaac: So my name is Isaac; I am 21 years old, and I study mechanical engineering at Antony. I’m starting my third year now. For R23, I was the composite production responsible for the aerodynamics group, and I joined Revolve because I wanted to learn more about cars and motorsports but also to apply the theory I learned in school in a practical project.

Peter: My name is Peter. I’m 22 years old. I started my fourth year in marine engineering at NTNU, and I was a fastener and fiber-sim responsible for R 23. The main reason I joined Revolve was to apply theory I learned in the practical project and to challenge myself.

Ebbe: So can you please tell us more about Revolve and the new, like what kind of organization is it and what do you set out to do?

Isaac: So Revolve NTNU is a voluntary student organization at Annu competing in Formula students. Each year we compete in three different competitions in Hungary, Austria, and Germany, and we build a race car each year. A new one. To compete in these competitions. And the main goal here is to develop students into engineers over one year.

Ebbe: So what is Formula Student, and what are the requirements for entry?

Peter: Formula Student is the world’s largest engineering competition, with about 1,000 teams competing and 30, 000 students. And in order to compete, all you need is a rules-compliant car. And you also need to do theoretical quizzes for each competition you’re going to, which will determine if you qualify. And also if, when you’re going to start scrutineering, and when you will do dynamic events.

Isaac: There are many different Formula Student competitions all around the world. We mainly compete in the European ones. Formula Student Germany is the biggest one and the most serious of them all. This is where the top teams compete. And each competition is divided into two parts. So you have a dynamic and a static part of the competition.

For the static part, you present your design and your manufacturing and your budgeting, as well as a business plan about your car. There are 3 presentations that each contribute to the overall score. Then you have dynamic events, where you have an acceleration event, a skid pad event, where you drive in circles to test your lateral capabilities of the car.

Then you have an autocross event, which is a single-lap shootout off the track. And then you have the endurance event, which is 22 kilometers or so of the autocross event. And this is also the event that gives the most points.

So it’s important to do well in the endurance event, as well as all the others. Combining the scores there, you get the overall score and the team with the best overall score, is the winner. Simple as that.

Ebbe: So there’s a lot of different competitions to prepare for. You have to have a rule compliant car. So how do you make that? What does that require from an organization? How many are you, and how are you structured?

Peter: Yeah, we’re usually about 63 people. Let’s start every year and be structured by the board being the main body. That is just the direction for the organization. And then we have four subgroups: marketing, mechanical, electrical, and software. And underneath these groups, again, we have subgroups, which are, for instance, aerodynamics, chassis, power systems, and so forth, which used to contain a group leader and five to seven group members that just worked on their system.

Ebbe: How is it to work in Revolve? Multidisciplinary environment, big team, different deadlines.

Issac: It is quite challenging, but also quite rewarding at the same time. You get to challenge yourself in many different ways, both in the aspect of time and also how to coordinate with so many different people and groups, but you also get a lot of friends and you get to know a lot of like-minded people so you can grow your network, and you also get to contact different sponsors, and you can potentially get a job there in the future, so overall it’s challenging and rewarding.

Ebbe: So please take us through a season in Revolve.

Peter: A season in Revolve usually lasts about 10 months, and it starts with two weeks of boot camp. And then two weeks of concept phase. And then we have about two months to design our system. And when we finish designing, we will do a quiz in order to qualify for competition. And then we will produce the parts we designed.

It usually takes about three months, and then we have unveiling, and then we usually work another month in order to get it test-ready. And then you have a test-ready car; you just start testing and get ready for competition. And then we have competition, which lasts about three weeks, is really hectic but definitely worth the entire trip, and it’s really fun.

Ebbe: So how many of the team go out to travel for these competitions?

Peter: Usually we are about 30 to 40 people, but depending on what we do during the summer, it can be a bit fluctuating numbers, but we can also charge to test the car during the summer and also prepare for the competition, but anyone can join.

Ebbe: Thanks for a great introduction to the Revolve Team student formula and how the season progresses. Let’s move on to the more technical parts of the interview. How do you make a car go really fast?

Isaac: So firstly, in motor sports, there’s a few principles you have to follow. The main one is to reduce the mass as much as possible. And the second one is to lower the center of gravity as much as possible. With these two in mind, you can build a very quick car.

In addition to this, you have to consider the purposes of your vehicle. Is it supposed to be very quick on the straights or very quick in the corners? For us, we drive very tight and twisty. Narrow circuits, so we will focus a lot on the cornering capabilities of our car. That’s why you see our car has a very short wheelbase and also very large wings to generate the downforce and grip. So the car can go quickly in the corners.

Ebbe: What is an aero package, and what does it do in those kinds of terms?

Isaac: The aero package is a collection of the wings and elements on the car to produce downforce and to guide the airflow. We use the aero elements to produce the downforce to increase the grip in the corners as mentioned, as this is something we found is the most important parameter for making the car go quickly. It’s like an upside-down airplane, really.

Ebbe: So why is downforce so important?

Issac: When you increase the vertical load of the tires, which is done by increasing the downforce, you increase the friction. It’s the same as basic friction theory. However, downforce can be considered as free grip, as you don’t have to move the extra mass. Why the wing elements are also made to be as light as possible, because the mass versus the downforce needs to be a good ratio on that one too.

Ebbe: How is the aero package then designed? How do you find the shapes and sizes of all of the wings?

Peter: It’s an iterative process. They usually start with basic theory and design the thing that’s going to work. And then they use CAD to draw it, and then they put it into STAR CCM, and then they get their results. And they can also postprocess these results to see where the air goes, where I have pressure, and so forth. And use that to then change their design and improve on it. That’s how we do aerodynamic design.

Ebbe: STAR CCM is known as CFD simulations, and what do you do with these simulations?

Peter: We usually compare them up against each other. After checking the residuals are okay, we put it into a large Excel sheet and then we compare the results. And then they see, did our change improve or make it worse? Did it improve airflow under the floor or did it improve airflow over the rear wing for instance? So what was the entire effect of the change we made?

Ebbe: So when you find your design, how do you know that it actually works?

Peter: This was the large focus this year, and that’s why we implemented the Pitot probe, which will measure the pressure on the nose of the car. And we also have a strain gauge system in our suspension, which will give us the forces acting on it. And based on the Pitot probe and the strain gauge system, we’ll get enough data to be able to validate our downforce and grip.

Ebbe: So when you have your wings, how do you manufacture them?

Isak:  The importance of weight and mass of the car is paramount, and that’s why we make our wings out of carbon fiber. And it’s a very light, stiff, and strong material, which will allow us to get the desired effects out of the elements.

So when we make them, we first have a mold that we shape to the part, and then we put the carbon fiber in it and then cure it under vacuum in an oven. So carbon fiber is very much like a fabric when it’s uncured, but when you cure it, it’s very stiff and strong.

Ebbe: Why do you want the wings to be stiff? They are only subjected to air, right?

Isak: Yes, but the aerodynamic loads—the loads from the air—can be very large. We have simulated over 800 newtons of downforce on the car, and that’s quite a lot considering the speeds we drive at, so we need the wings to be able to withstand all this force that it produces.

Ebbe: So thanks for outlining the most important factors of the aero package. So we can move on to the component known to you as the shark fin. So what is a shark fin? What does the name come from?

Peter: Shark fin is the new concept we looked for at the rear wing fastening. And it’s called shark fin because it looks like a shark fin on the rear of the car. And it’s supposed to be a more aerodynamic part this year compared to previous years. So it improves the airflow. We’re still able to have the same rigidity. So we don’t have as much compliance from aerodynamic loads.

Ebbe: So how does it improve the air flow? What do you mean by that?

Peter: It improves the airflow in many two ways. One way is that it reduces the vortex generation underneath the wings. So the flow is much more attached under the rear wing. And also when we’re cornering this. generated a vortex from the high pressure to the low pressure side of the shark fin, which is then pushed over the rear wing, so it will not affect the wing package.

Ebbe: So you mentioned that the shark fin is also carrying the whole rear wing, meaning it’s a lot of load going through the shark fin. So how do you ensure that it’s stiff enough to withstand all these loads?

Isak: So the structural design of the shark fin is done in Abaqus finite element software that we use to model the shark fin itself as well as the rear wing. And we also introduce the different wires that we have on the car to try to simulate it as close to reality as possible.

First, we have to look at the different loads that it needs to withstand. We have different rules that mandate certain loads, as well as the aerodynamic loads. And then we do simulations on both loads and see which is the deciding factor for the stiffness of the shark fin.

For the aerodynamic loads, we took the pressure distribution from CFD, put it into Abaqus, and simulated the deflection from the arrow. We then re introduced the deflection into Star CCM and simulated the CFD with it, and then saw how much losses we had from it. And then this changed the layout based on that. Yeah. So it’s a very simple approach to get some results out of it. Not the optimal, but it is a good approach.

Ebbe: So we have a subset of requirements, meaning that you need to consider loads that you might be subjected to under rules and regulations and also aero loads that you have from the speeds and scenarios you are driving in. And then you are basically trying to include as many components as possible to find the lowest possible math to give you the stiffness you need. To go more into the basics. What is the key thing to focus on when you Make a good shark fin? What is the main objective?

Isak: So firstly, we have to consider the main task of the shark fin, and it is to fasten the rear ring. It must be stiff enough for the rear ring to be in its place and to produce the downforce it needs. And secondly, it needs to act as an aerodynamic element.

We have the fastening done, so we know the rear ring is good. Then we can start iterating on the aerodynamic properties of it, like its shape. And after that, we go back to the structural software and see if we can make it stiff enough with the different uses of carbon fiber, putting the fibers where we want them and optimizing around that.

Ebbe: So thanks for taking us through the design iteration process for the shark wing and how to ensure that it is able to sustain the loads it will be subjected through. How is the competition season going?

Isak: It’s been quite nice. It has been one of the better seasons. We finished all three endurance events this year and we had a first place in efficiency and a first place in autocross, as well as the first place in driverless acceleration, among other second and third places. So it’s been a very successful season. Not exactly where we want to be. Our goal is top 3, but we couldn’t do it overall this year. So we will see what happens next year.

Ebbe: There’s always next year. So how do we follow you guys in terms of social media and building the car? And how do you follow you when you are competing? How do we get to see the events?

Isak: You can just look up Revolve NTNU on whatever social media platform you have. Or you can go to revolve. no on the internet and you will find contact information and links to all of our social media there. We will also post regular updates there about how the project is going, especially through YouTube. You’ll find vlogs where people post some clips of their work, and you’ll see how the project is going. We also give updates on the competitions on social media.

So if you’re eager to see how the car drives, you can always go on YouTube and look up at different competition and you’ll see it, or you can go and check out Instagram. There’ll be videos there too.

Ebbe: So we in TECHNIA think it’s always fun to follow the project from basically start to end, and big thank you for a great year and good results. You should be really proud of what you have achieved. And we’re looking forward to even more collaboration for next year. And it’s been a pleasure to follow and work with you and big thanks for taking the time to share your knowledge and experiences from this year. Big thank you. And thanks for watching.