Aeronautical Wind Tunnels. Achitecture, Testing Process, Measurements Techniques

A wind tunnel is a facility for aerodynamic experimentation, designed to reproduce in the laboratory the physical phenomena occurring in the flow of a fluid around an object.

Despite the fact that the fundamental laws governing fluid motion (Navier-Stokes equations) were formulated as early as the 19th century, throughout the 20th century experimentation was virtually the only reliable method for making aerodynamic predictions at key points in the aircraft flight envelope. . It was during this period, and particularly after the Second World War, that wind tunnels and associated measurement techniques were developed and perfected, many of which are still in use today.

Wind tunnels have contributed to our understanding of the physical phenomena involved in flow. These phenomena could then be modeled and integrated into mathematical models. The growth in computing power has made it possible to implement models that are increasingly close to reality, to the extent that numerical simulations are now an essential tool for aerodynamic design. As a result, experiments and simulations look set to coexist, or better still collaborate, in the decades to come.

Even if the physical phenomena involved in the many aerodynamic applications (automotive, construction, sports, etc.) are partly the same, different needs have led most wind tunnels to specialize in a specific area of testing. This article will therefore focus on aeronautical wind tunnels, designed for aircraft testing.

Predicting the behavior of an aircraft during its design phase, before it is built and put into flight, meets several objectives: guaranteeing the safety of the aircraft during its mission, optimizing its performance and, lastly, predicting the nuisance it causes to its environment. In all three respects, a reliable, accurate forecast helps to reduce design margins, making the product more competitive in a largely global market. The earlier in the development program that this forecasting takes place, the more effective it is, since it is then possible to modify the design without incurring significant additional costs.

Wind tunnels play an essential role in the aerodynamic part of these forecasts. They thus represent a strategic investment that has been essential to the success of past aeronautical programs, and should remain so in the future.