Wind tunnels allow the characterization of the aerodynamic attributes of objects in a controlled system by creating airflow through a closed passage. They are primarily used in the study of how aircraft, trains, automobiles, boats, and structures interact with aerodynamic forces. Wind tunnels operate on the principle that air moving past a stationary structure produces the same effects as an object moving through stationary air, facilitating practical research opportunities. Air is typically moved by a series of powerful fans and is mixed with smoke, suspended particles, or oil to visualize aerodynamic effects.
A vehicle within a wind tunnel, showing a visualized airstream.
Image credit: SeriousWheels
Wind tunnels are typically classified by the wind speed they allow, from low-speed (up to 480 km/h) to transonic (up to Mach 1.2) tunnels. Specialty tunnels, some of which employ pressurized gases, cryogenic temperatures, and high altitude effects, are also used.
Construction of a large wind tunnel; the structure to be tested would be placed on the gray circle at center.
Image credit: F1Technical