Wind Tunnel

A wind tunnel is an apparatus that produces a controlled stream of air past a stationary test object, reversing the usual relationship of a vehicle moving through still air so its aerodynamic forces can be measured safely and repeatably. Eighteenth-century experimenters such as Benjamin Robins and George Cayley had tried spinning objects on a rotating arm to study air resistance, but the arm's own wake and centrifugal effects distorted the results; the English engineer Francis Herbert Wenham resolved those problems by building the first enclosed wind tunnel in 1871. The Wright brothers used a wind tunnel of their own design in 1901 to refine their aircraft's wing shapes, and Gustave Eiffel later built a wind tunnel in Paris in 1909 where he ran some four thousand systematic aerodynamic tests.