Key challenge is wind tunnel: why F1 development is becoming increasingly difficult

10/06/2024 10:23 AM

The 2024 Formula 1 championship is entering its final stages, with the title race still wide open. After a strong start, Red Bull has started to fall behind, partly due to correlation issues between the wind tunnel, simulation tools like CFD, and the track, with the team now trying to recover and inject new energy into the world championship battle.

However, the issue of missed correlation doesn’t only concern Red Bull. A key aspect of this season has been the development difficulties faced by several teams throughout the championship. Ferrari, Mercedes, Aston Martin, and Racing Bulls, for example, had to revert some specifications after encountering correlation issues with the new packages introduced mid-season, as they pushed for more aerodynamic downforce, often facing an old enemy: bouncing.

Developing these cars is becoming increasingly complex, and the challenge is no longer just about finding pure aerodynamic downforce but, above all, about achieving the right balance to maximize the car’s performance and give the drivers confidence in the vehicle. It's no coincidence that, for example, McLaren has taken a more cautious approach to upgrades, introducing packages only when they are fully satisfied with the wind tunnel results, with the floor—arguably the most sensitive element—remaining unchanged for several races.

With these ground-effect cars gradually reaching their limits, finding more downforce is proving to be a double-edged sword, as the risk is encountering unwanted effects. But why is it becoming more and more difficult to extract that extra performance from the wind tunnel and simulations, sometimes facing correlation problems?

First, it's worth taking a step back to the method teams use to predict bouncing, that extremely tedious phenomenon with this generation of cars that is, however, very difficult to replicate during the development phase in the factory. Teams also rely on simulations and other tools to try to predict bouncing, using the data accumulated throughout the season. But when trying to change the floor design or add more downforce, the risk is that the algorithms don't reveal the truth of the track.

“Even by regulation, it's not possible to simulate bouncing in the wind tunnel, so you have to find some sort of semi-empirical or fully empirical metric, which is ultimately based on physics but functions like a simulation. So, we still try to have a base of experience to work from,” explains Simone Benelli, Principal Aerodynamicist at Haas.

“But when you completely change the floor concept, like we did at Silverstone, you have to trust that the experience built on a different concept is still valid. So, it's not simple,” he said, referring to the fact that the American team brought its second major technical package of the season to Silverstone, also modifying the floor to improve the car in high-speed sections, where it had shown some weakness earlier in the championship.

“Other aspects, such as low-speed behavior, are very difficult. Obviously, the wind tunnel model is in 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 of it, creates a wake at the front with a yaw angle. That wake travels and hits the rear with a different angle.”

In the wind tunnel, teams have rotating platforms that allow them to move the car relative to the headwind, simulating different scenarios to understand the behavior of the airflow in corners, where instability problems often arise. 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 works even “in motion” allows for a large amount of data to be collected, simulating how the airflow changes.

With these ground-effect cars, though, the issue of floor proximity to the asphalt is becoming increasingly critical, especially when teams are chasing the last few tenths of performance. It's difficult to simulate these aspects in the wind tunnel, as the risk is damaging the tunnel's floor. It's no coincidence that several manufacturers are investing in state-of-the-art facilities, like different materials for wind tunnel carpets, or even entirely new ones. Ferrari used the summer break to work on this front, while McLaren and Aston Martin have developed upgraded facilities, a path followed by Red Bull, although the Milton Keynes team won't be ready until 2026.

One of McLaren’s crucial aspects is that they have managed to find downforce over time but also maintain good balance without encountering bouncing. “I think some teams experience it more than others. We see it, but it doesn't seem to affect us significantly 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 any condition where the car touches the ground, it's not something that's easy to simulate in the wind tunnel because you risk damaging both the scale model and the wind tunnel itself,” adds Benelli, with Haas making use of Ferrari's recently upgraded wind tunnel. Although teams try to obtain a complete map of the car, understanding the car's behavior in different conditions, when reaching high speeds and loads—where bouncing typically occurs—it becomes difficult to get a full picture. That's why teams also try to cross-check wind tunnel data with simulation tools, but the closer they get to the limit, the more they rely on the tools’ ability to predict the car's behavior or the presence of bouncing.

“So, we try to maximize map coverage. This way, you get a portion of the track covered by the wind tunnel's aerodynamic map, but with this generation of cars, it's very difficult. In the past, it was almost complete—maybe at the end of the straight you couldn't manage it, but in any case, it didn't matter to us. This time, high-speed corners are sometimes impossible to replicate in the wind tunnel.”

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