Wind tunnels still play a critical role in a car's success on the track

Modern day Formula One cars are now more sophisticated than ever and to be a successful team requires the use of the latest tools during the design and development stages. The wind tunnel is one of these tools and plays a critical role in a car’s success on the race track. With two tunnels at Williams, we talked to our Head of Aerodynamics, Jon Tomlinson to unravel some of the tunnels’ complexities.

"A wind tunnel is a research tool which assists in the study of the effects of air moving over and around solid objects. They were originally developed for some of the first experiments in aviation theory, such as determining the lift and drag of various airfoils. The Wright brothers used a simple wind tunnel in 1901 to study the effects of airflow over various shapes while developing their Wright Flyer. Subsequent use of wind tunnels proliferated as the science of aerodynamics and the discipline of aeronautical engineering were established."

"Wind tunnels work by either blowing or sucking air through a duct equipped with instrumentation where a model is mounted for study. Typically the air is moved through the tunnel using single or multiple fans. Due to the sheer volume and speed of air movement required, the fans need to be extremely powerful. There are several ways in which the air flow can be studied: from simple flow visualisation techniques such as using smoke or wool tufts attached to the surface of the body; force measurements using a model mounted force balance (measuring lift, drag, pitching moments); to pressure measurements across the body's surface by use of pressure taps."

"The use of wind tunnels for aerodynamic testing in Formula One can be traced back to the 1960s but it wasn't until the late 1970s that teams really started to understand the importance of aerodynamics. Today, to test and develop the aerodynamics of their cars, teams spend vast amounts of time using wind tunnels. Typically, teams use a scale model of the car for testing purposes, although a few teams now also have the capabilities to test the actual race cars in their wind tunnel, including Williams."

"Wind tunnels in Formula One are usually closed tunnels (in that air circulates around in a continuous closed loop) and require massive fans to push the air around the tunnel at speeds of up to 80m/s (288kph). The air flows around the tunnel until it approaches the test section where the model of the car is held. At this point it travels through a contraction section which speeds up the air. The model is typically held rigid in the test section by means of a vertical strut, with a force balance located in the model to measure the forces applied due to the air flow.

"As well as air being blown over the car, to simulate the air flow around the car accurately also requires the use of a rolling road. In simplistic terms this is similar to a large conveyor belt, but runs at much higher speeds to match that of the air speed. It is this moving belt that simulates the race car moving along the ground, which is particularly important with Formula One cars that are working in such close proximity to the ground. This also enables accurate flow to be simulated around the wheels, as they are then able to rotate with the speed of the belt.

"During each test run it is common for the model to be moved into different heave and pitch positions to simulate the attitude that the race car experiences during the course of a lap. The model can also be tested at an angle to the wind, which allows the aerodynamicists to measure the effect of cross winds - therefore simulating what happened when the car corners. Force measurements are taken at all these conditions and it is from these that the aerodynamicists are able to analyse the aerodynamic performance of the car and its sensitivities to various conditions. This analysis enables geometry changes on the car to be evaluated and changes to be made to improve the performance of the car.

"It is clear that wind tunnels have become a significant tool in the design and development of modern day Formula One cars and although computational methods (CFD) are improving at a rapid pace, they are still very much a supplement to the experimental work in a wind tunnel and are unlikely to replace what can be achieved in a wind tunnel for many years to come."