Nick Wirth of Manor says that he is not going to do ANY wind tunnel testing for his 2010 Formula 1 car, arguing that computational fluid dynamics (CFD) is now good enough to do all the work by computer. He argues that as a result less effort is going to be wasted on traditional aerodynamic research and thus, logically, more development will be done in the time available. Most F1 teams understand the value of CFD but use it in tandem with the traditional methods and argue that each technique brings different things to the party and that the best result is to develop cars with a combination of the two.

The wind tunnel has been used since very early on in the history of aviation and simulates the movement of an object (a car or a plane) through air. If one mounts the model on a suitable balance, the forces being generated can be measured.

The problem is that air through which F1 cars go is rarely undisturbed and so to master the effects of turbulence is difficult. The F1 teams long ago developed rolling roads so that they could study the interaction between the cars and the ground and they have also developed ways to minimise the effect of the walls on the testing. There are also questions of temperature created by the windtunnel itself which will affect the way the air behaves. Thus Red Bull Racing, for example, uses a massive solid concrete tunnel at Bedford that is not affected by such things. It has recently emerged that Chip Ganassi Racing has been using a different and more cost-effective method of aerodynamic research by running cars under their own power through a disused road tunnel in Pennsylvania. This is a lot cheaper than building a vast wind tunnel facility and cars can be tested in whatever temperature one chooses to test them in.

The boffins, however, have long argued that the best method of testing will be CFD in which all the elements can be simulated and measurements can be made without the need to solve problems that wind tunnels create. They argue that it is faster and cheaper because virtual models are much more efficient and less complicated than creating physical models. The problem is that CFD makes assumptions and approximations and this is a problem, particularly when engineers try to model air turbulence. Computer modelling uses what are called meshes, which consist of millions of cells each programmed to behave in a certain way when pressures are applied. These then combines to visualise flows and so on. The modelling of F1 cars involves massive meshes and so require huge computing power if they are to be fast and efficient. The development of CFD has been ongoing for more than 25 years but in that time wind tunnels have also improved with such new ideas as pressure-sensitive paint and the much faster manufacturing techniques for models resulting from stereolithography and other similar techniques. Most F1 teams use both CFD and windtunnels in order to sort out the limitations and anomalies that exist in one method but not in the other. CFD, for example, can model the air in a large area around the car. Physical scale modelling provides a more immediate view of the external air flows, but CFD methods allow the study of internal flows and such things as heat transfers. With CFD, however, the problem of external turbulence is considerable whereas a wind tunnel model can be run in tandem with a second model and lessons can be learned with relative ease. The CFD developers are gradually working on this.

There have been some interesting examples of vehicles developed only with CFD, notably SpaceShipOne, a private rocket-powered aircraft that completed the first private space flight in 2004. This was developed by Burt Rutan’s aviation company, which is today developing Virgin’s planned commercial spaceships. Given that there is a tie-up between Virgin and Manor F1 this may be part of thinking behind Wirth’s attitude to CFD.

It should also be noted that Aston Martin did not use a wind tunnel at all when developing the DBR9, the racing version of the DB9, deciding instead that the CFD programme “Sculptor” was sufficiently good enough for the job. This programme was created by Optimal Solutions Software in Idaho. This was seen as a major turning point for the CFD industry and showed that CFD had come of age when the DBR9 took class victory on its debut at the Sebring 12 Hours in 2005, beating the factory Chevrolet Corvettes. It was probably this that resulted in the decision of BMW Sauber not to follow the F1 trend and build a second windtunnel but rather to invest in a supercomputer, capable of much higher levels of calculations than some of the existing equipment.

“The big difference with CFD compared to wind tunnels is that you not only get results but also get an understanding of what goes on,” explained Mario Theissen at the time. “Wind tunnel testing remains important with experimental work and CFD complementing each other.”

In 1996 I went to Ford’s Advanced Engineering Center in Dearborn, Michigan and reported that “the computer simulation laboratories are constantly developing new forms of computer aided engineering, which will be of great advantage to F1 teams as research and development can be done faster – and therefore cheaper. This is particularly useful in areas such as computational fluid dynamics (CFD) and thermal and aerodynamic systems engineering (TASE).The systems are advancing at such speed that computational wind-tunneling will soon be so sophisticated that it will probably not need to be verified in windtunnels.”

That was 13 years ago and the development of CFD has been a lengthy and expensive process. According to Moore’s Law, the power of computers has been doubling every two years and thus the best current computers should by now be able to do 64 times as much as they did in 1996.

A year from now they should be 128 times more powerful.