The Honda wind tunnel

Success or failure in Formula One today is governed by the car’s aerodynamic performance. With less than a second covering the first five places on the grid, the efficiency of a front wing endplate is just as important as the driver’s technique or the horsepower of the engine. Tiny revisions can have huge consequences, which is why the Honda Racing F1 Team has invested around £30m in a new, full-scale wind tunnel at the team’s headquarters in Brackley, England.

The three main components of an F1 car’s performance are the tyres, the engine and the aerodynamics. In recent years, the Formula One regulations have become more complex and restrictive, placing a greater emphasis on aerodynamic efficiency and attention to detail.
The cars are now more sophisticated than ever before and to be successful, the designers need the latest tools. The new, state-of-the-art wind tunnel will play a critical role in the Honda team’s future.

The use of wind tunnels for aerodynamic testing in Formula One can be traced back to the BRM team of the 1960’s but it wasn’t until the Lotus ‘ground effect’ cars of the late 1970s that teams really started to understand the importance of aerodynamics. By today’s standards, even the turbocharged cars of the mid-1980s were relatively crude.

“Now we have a very competitive Formula One environment with some very clever people, who are well resourced and organised,” says Chief Aerodynamicist, Mariano Alperin-Bruvera. “In the past 10-15 years, the rate of progress of the cars has been largely constant, but the amount of effort that’s gone into achieving that has probably increased ten-fold because we’ve become much better at designing race cars.”

Anyone taking a peek at the specification of the three-storey building that houses Honda’s new wind tunnel will be left in no doubt about the team’s commitment. Approximately 5.5 km of concrete piling was installed, weighing 6000 tonnes. More than 160 tonnes of reinforcement was used in the slab and bases, with half of the slab designed to withstand the load of a 250-tonne crane.

The wind is generated by a huge fan, consisting of sixteen rotating, composite blades and 27 stator (static) blades, which are made of steel. Each blade is 5.3m long with a hub diameter of 2.4m. This fan is powered by a 3035hp electric three-phase induction motor generating an astonishing 32,125lb ft of torque at 495rpm. During a test session, this giant construction will move 895m3/sec of air to generate a wind speed of 80m/sec. That this highly complex, technical structure was completed in just 18 months is a testament to the skill, dedication and teamwork of the construction engineers.

The scale of the enterprise reflects Honda’s decision to construct a full-scale wind tunnel, capable of accommodating a real grand prix car. Until now, the team had relied on testing quarter or half-scale models of the chassis. These tunnels had relied on a useful bit of physics, which dictates that the air flow over a car is described by the speed multiplied by the length. If you halve the length of the car and double the wind speed, you can achieve reasonably accurate results.

But in today’s highly competitive environment, ‘reasonably accurate’ is no longer good enough. The team had achieved as much as it could with a half-scale model and now needed to be able to resolve more subtle differences.

If the Formula One rule-makers continue to restrict the number of days that a team may test at a circuit, wind tunnels and computer simulations will become even more important. “We’ll need to do our testing in what you might call laboratory conditions,” says Alperin-Bruvera. “If you test at a track and there’s wind or rain, you could easily lose a day’s work.”

The wind tunnel is an important component in a testing chain. Parts are designed using CAD (Computer Aided Design) technology and then tested using CFD (Computational Fluid Dynamics) software. The latter uses sophisticated computer processing to analyse the likely impact of a new part before it is manufactured. Parts that show a benefit on the computer will be built and tested in the wind tunnel.

If the tunnel analysis proves successful, they will be tested ‘for real’ on the car. “The tunnel won’t stop us taking aerodynamic measurements at a circuit,” explains Alperin-Bruvera, “but it will help us understand the subtleties of the kits before they’re given to our drivers.”

A wind tunnel is a stylised version of what happens in the real world. The car is held still, while the road and the air are moved. The car can be tested at an angle to road and at an angle to the wind. This allows the aerodynamicists to measure the affect of cross winds and the yaw rate - what happens when the car corners.

Wind tunnel technology has improved dramatically in recent years, but it does have its limitations. It’s impossible, for example, to simulate gusting wind or the affect of the air flowing across rough surfaces, such as grandstands or grass. The human element is also critical. The technicians must understand the tunnel’s limitations and use it in the right way. This is something that some teams do better than others.

It is impossible to underestimate the complexity of the work. On a modern F1 car, the aerodynamics increase the mechanical grip - provided by the tyres and suspension - by a factor of two or three. Put simply, the aerodynamics force the car into the ground, allowing it to corner at a higher speed. A modern F1 car can corner at 4.5G and brake at 5G. At 100mph, it could drive upside down.

One of the biggest challenges facing the engineers concerns the interrelation of the parts. The way the regulations have evolved over the past few years has made all the elements interact more strongly. Changes to the front wing, for example, affect the sidepods and rear wing. Each circuit also requires a unique set-up. The aero kit for a high speed track such as Monza will be dramatically different to the one needed in tight, twisty Monte Carlo.

This emphasis on downforce differentiates a road car from a racer. Road car aerodynamicists are interested primarily in limiting the aerodynamic drag to reduce fuel consumption and wind noise. The shapes are more slippery - the drag coefficient of a Honda NSX supercar is about three times better than a Formula One car, which has more in common with a house brick. But a road car doesn’t generate anywhere near as much downforce. Even the very best road going sports cars only generate about 20% of their grip from aerodynamics.

The road and race teams therefore work to very different targets, but the tools and techniques they use are very similar. This allows the teams to share their experiences and learn from each other.

The Honda Racing F1 Team’s new tunnel is capable of operating 24/7 and will be used in conjunction with the team’s current, half-scale tunnel. Both are a potent illustration of Honda’s commitment to Formula One and of the team’s pursuit of performance.