The 2024 championship is entering its final part, with a challenge for the title still completely open. After a leading start to the championship, Red Bull began to slip backwards, also due to correlation problems between the wind tunnel, simulation tools such as CFD and the track, with the team now trying to get back on its feet to give new life to the world struggle.
However, the issue of lack of correlation does not only concern Red Bull, because one of the key aspects of this season was precisely the development difficulties that various teams encountered during the championship. Ferrari, Mercedes, Aston Martin and Racing Bulls, for example, went back on some specifications after encountering correlation problems with the new packages introduced mid-year, when they increasingly went in search of aerodynamic load, often clashing with an “old” enemy, bouncing.
Developing these cars is becoming more and more complex and the challenge is no longer shifting to just finding the pure aerodynamic load, but above all to finding the correct balance, in order to make the car perform at its best while giving the drivers the right confidence in the single-seater. It is no coincidence that, for example, McLaren has chosen a more cautious approach to the new features, introducing packages only when it is completely satisfied with the results in the wind tunnel, so much so that the surface, the most sensitive element, has remained unchanged for several appointments now.
The Red Bull wind tunnel: the team is building a new structure in Milton Keynes to replace the current one, which is now too many years old
Photo credit: Red Bull Content Pool
With these ground effect cars slowly approaching the limit, finding more load is proving to be a double-edged sword, because the risk is having to collide with unwanted effects. But why is it now becoming increasingly complex to extract that something extra from the wind tunnel and simulations, sometimes running into correlation problems?
First of all, it is good to take a step back to the method with which teams try to predict bouncing, that extremely tedious phenomenon on this generation of single-seaters which, however, is extremely complex to replicate during the development phase in the factory. Teams also rely on simulations and other tools to try to predict bounces, taking advantage of the data accumulated over the course of the season. But when you try to change direction on the surface, perhaps with a different design or by adding even more load, the risk is that the algorithms do not return the truth of the track.
“Even by regulation, it is not possible to simulate bouncing in the wind tunnel, so you have to find some sort of semi-empirical or fully empirical metric, which ultimately is based on physics, but it is like a simulation. So we still try to have a base of experience to work on,” explains Simone Benelli, Principal Aerodynamicist at Haas.
“But when you completely change the concept of the fund, as we did at Silverstone, you have to have confidence that the experience built on a different concept is still valid. So it’s not simple”, he explained, referring to the fact that the American team brought its second major technical package of the season to Silverstone, also intervening on the floor to improve the car in those high-speed sections, where at the beginning of the championship it had shown some signs of weakness.
McLaren has renewed its wind tunnel, now one of the strong elements of the Woking team
Photo credit: McLaren
“Other aspects, such as low-speed behavior, are very difficult. Obviously the wind tunnel model is pure yaw. So any curvature, the fact that the front wing sees the wind from the inside, while the rear of the car sees much less. A wake is generated on the front with a yaw angle. That trail travels and hits the rear at a different angle.”
In the wind tunnel, in fact, the teams have rotating platforms that allow them to move the car with respect to the direction of the frontal wind, in order to simulate different conditions and scenarios and understand the behavior of the flows in corners, where we tend to often talk about problems of instability. For example, at Sauber in Hinwil this system that allows the car to rotate in the wind tunnel has existed for several years, albeit with a limited angle: however, the fact that it also works in “motion” allows you to obtain a large quantity of data by simulating how the flows vary.
With these ground effect single-seaters, however, the issue of the proximity of the surface to the asphalt becomes increasingly key, especially when you are looking for the last cents in terms of performance. In the wind tunnel it is difficult to simulate these aspects, because the risk is to destroy the floor of the tunnel itself: it is no coincidence that several manufacturers are equipping themselves with cutting-edge structures, such as carpets made of different materials and investing in completely new ones. Ferrari took advantage of the summer break to work on this front, while McLaren and Aston Martin have created renovated structures, with a path also followed by Red Bull, although the Milton Keynes team will not be ready before 2026.
Ferrari wind tunnel
Photo by: Ferrari
One of the crucial aspects of McLaren is that it has managed over time to find load, but also with a good balance, but without encountering bouncing: “I think some teams experience it more than others. We see it, but we don’t seem to have suffered particularly from it, if it limits us in terms of performance. I think it’s probably on the verge of limiting us, but we don’t suffer from it,” said Rob Marshall, McLaren’s technical director.
“Obviously, in all the conditions in which the car touches the ground, it is not something that is easy to simulate in the wind tunnel, because you risk destroying both the scale model and the tunnel itself,” adds Benelli, with the Haas which takes advantage of the recently renovated Ferrari wind tunnel. As much as we try to obtain a complete map of the car, understanding the behavior of the car at different ranges, when high speeds and loads are reached, where bouncing generally occurs, it becomes difficult to obtain a total vision. For this reason we also try to cross-reference the wind tunnel data with simulation tools, but the closer we get to the limit, the more we rely on the tools’ ability to predict the behavior of the car or the presence of bouncing.
“We therefore try to maximize the coverage of the map. In this way you obtain a portion of the track actually covered by the aerodynamic map in the wind tunnel, but with this generation of car it is very difficult. In the past it was almost complete, maybe we couldn’t make it to the end of the straight, but in any case we weren’t interested. This time, the high-speed corners are in some cases impossible to replicate in a wind tunnel.”
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