Wind tunnels are at the core of aerodynamic development. They work by mounting an object in the middle of a test section, where a controlled airflow is blown on the model. The air is moved by one or more fans and directed through to the testing area via air-straightening devices.
For automotive and motorsport purposes, subsonic closed-return circuit tunnels are commonly used. The air flows into a closed circuit, where it's moved by fans and guided around corners by turning vanes. The air is then stabilised through honeycomb screens, accelerated through a nozzle into the test section and guided back into the fans.
The test section design should allow to replicate free-stream conditions. This is achieved by ensuring the wall design is correct, which will minimise interference. Additionally, the absence of a boundary layer on real roads requires devices that minimise the boundary layer on the floor of the wind tunnel's test section. Therefore, wind tunnels used for motorsport and automotive testing must be equipped with a rolling road, which is synchronised with the airspeed, and with a boundary layer suction system.
Effective wind tunnel testing of racing cars further requires an extremely precise model support and positioning system, which allows to simulate the heave, yaw, roll and pitch movements that the real vehicle will experience on-track. Additionally, careful attention is paid to wheel simulation, due to the strong influence they have on the overall aerodynamic performance. To suit customer's preferences rolling wheels can be directly attached to the model or supported by external struts.
The main acquisition system – the balance – measures the forces and moments acting on it. Additional information is usually recorded by wheel and wing balances, as well as pressure taps on the model's underbody, bodywork and cooling devices.