Exa CFD software for Formula 1: The digital wind tunnel

W ind channels are expensive. No new ones have been built for years. At most old ones modernized. Teams like McLaren or Force India are switching to existing plants like Toyota's because it's no longer worth renovating their own. The point is foreseeable at which the wind tunnel will no longer be needed. In many engineering offices, CFD simulation has already overtaken the wind tunnel. CFD (Computational Fluid Dynamics) is the digital representation of flow conditions.

Force India Technical Director Andy Green admits: “With CFD we get a better idea of ​​what is really going on in the car compared to the wind tunnel model. Previously the ratio was 60:40 in favor of the wind tunnel, now it's the other way around at around 70:30 for CFD. We are now extremely dependent on CFD, because you can recognize things on the computer that it is impossible to see in the wind tunnel. ”In addition, wind tunnel tests cost money, cost time and tie up a lot of staff. A change must be made to the model for every modification.

From series development to motorsport

Many teams have developed CFD software themselves and adapted it to their needs. But there are now also external providers. One of the largest is the US company Exa from Burlington. Exa originally developed simulation software in the car sector for automotive groups. Customers include BMW, Fiat, Chrysler, Ford and Honda. But motor sport also became interesting for Exa step by step. There the development speed is higher and with it the need for software.

Exa supplies the basic software called Powerflow for racing teams in Formula 1, WEC, DTM, the US racing scene and Formula E. that can be individually upgraded. For this purpose, the software provider also provides customer advisors. The first contact with motorsport came through BMW. A Formula 1 racing team has made significant progress in the field of aerodynamics with the help of the digital wind tunnel. For less money than before.

In motorsport, however, it's not just about finding the last tenth of the lap time. In almost all racing series, you rack your brains over how to improve the show. Overtaking has become a problem because of the increasingly sophisticated aerodynamics. We are looking for ways to reduce the aerodynamics so much that, on the one hand, the individuality of the cars is notis lost, on the other hand two cars can drive close behind one another.

It's faster in bits and bytes

The DTM has already made a successful start. Many of the little aero aids that make the air worse for the car behind have been abolished. BMW commissioned Exa to find out how the M4 is still drivable and competitive with 30 percent less downforce. The US company had developed a digital platform on which the flow conditions of two cars can be displayed one behind the other. In this way, solutions can be developed to offer the following car clean air.

Exa is now also in business with the new Formula 1 owners. Cars are to be built here in two steps, with which wheel-and-wheel battles are possible again. The downforce loss for the following car should be minimized. The first step towards this will be seen in the 2019 season. Front wings and brake ventilation are simplified, the air flow is no longer directed outside the car, but inside.

CFD simulations have shown that in the current cars, all harmful turbulence behind the car comes together again exactly where the front wing of the car behind is located. For the pursuer, this means a loss of downforce and, as a result, less grip from the tires. This process is expected to be completed in 2021. Then Formula 1 will get a completely new face.

The digital representation of 'dirty air' helped with this work because it was for the first time visible what was happening behind a racing car, both on the straight and when cornering. And what influence that has on the pursuer's aerodynamics. While you would have to put two cars one behind the other in a wind tunnel and laboriously find out in many test series under which conditions the following car gets bad air, the computer can be used to move the distances and the positions of the two cars to one another as desired and the consequences of this can be made visible. It's faster and cheaper in bits and bytes.