Long before their birth, scale models of the actual F1 cars are tested and evaluated in the team’s’ wind tunnels.
A wind tunnel is a tool used in aerodynamic research to study the effects of air moving past solid objects. It consists of a closed tubular passage with the car to be tested mounted in the middle. A powerful fan system moves air past the car; the fan must have straightening vanes to smooth the airflow.
|Fan of the Red Bull Technology wind tunnel. (Photo: Red Bull)|
There are in fact two main types of wind tunnels. One type is called an “open circuit tunnel”s with an air entry open to the atmosphere. Formula 1 teams rely on the other type:, the closed circuit wind tunnels. These generate a more uniform flow, in principle, than open circuit tunnels.
They are said to be low-speed closed circuit tunnels. This means that the speed varies between 10 and 100 m/s approximately, and the same air is recirculated. The stream is turned, typically by four 90° corners, each provided with turning vanes placed aside of each other, to prevent turbulence in the corners.
Highly skilled members of the aerodynamic department build scale models of the actual car, complete with wheels, suspension, wings, and driver’s helmet. It is made of a stiff skeleton on which the various parts -- made of aluminium, plastic or carbon fibre -- are bolted or glued. Rapid prototyping makes it relatively easy to produce small component thatare can be quickly evaluated in the wind tunnel.
Since the model parts do not represent the real- world car size, a Reynold’s number is , for example, used to make coefficient correlations between the model parts and the 100% to-scale model. A Reynold’s number is a measure of the ratio of inertial forces to viscous forces.
The model car is placed in the test chamber of the wind tunnel. It rests on a rolling road thatwhich is designed to simulate the track. The idea is to make the track move under the car at the same speed thatas the air flows around the car, complete with rotating real tires. Wheels that rotate at 300km/h produce a lot of turbulence.
|Ferrari wind tunnel in Maranello. (Photo: Ferrari)|
Once the fan is started, and the wind it produces simulates how the real car in motion would flow throughin the air while running on the road course.
Aerodynamic forces applied on the test model are usually measured with beam balances, connected to the model with beams, strings, or cables.
The direction of airflow on the surface can be visualized by taping threads on the test model. Smoke can also be introduced into the airflow upstream of the test model. Or Flow-viz can also be applied on various the parts and its path around the model can be examined afterwards. Pressure-sensitive paint, in which higher local pressure is indicated by lowered fluorescence of the paint at that point, is also used.
The test model is attached to a vertical beam that can move in several directions. This beam is used by the engineers to move the model in relation to the ground in order to simulate yaw (as if the car was into the cornering), pitch (as if the car was braking or accelerating), and to adjust ride height with a precision of 0.01 mm. The movements of the model car are controlled by a computer.
Interestingly, the suction generated by the floor and diffuser of the car creates is so great that the rolling road must the sucked down by a vacuum so it remains perfectly flat!
|Scale model of a Formula 1 car being tested in the wind tunnel. (Photo: Toyota TMG)|
In order to reduce the costs, the FIA has put restrictions on wind- tunnel testing. The scale models used cannotmay be anyno larger than 60% of a full- size car, and speeds are limited to 50 metres/second (which translates into 180 km/h).
Results from the wind tunnel are then compared with the data obtained during straight- line aerodynamic tests on an airfield. Teams are allowed to perform four days of aero test during a full season.