What Is a Wind Tunnel?

Wind tunnels are structures used in aerodynamic research that enable scientists to study the effects of air on stationary objects. This is useful in the manufacturing of airplanes and cars, as well as in the construction of tall structures like buildings and bridges. Once scientists know how a certain object will react under simulated conditions, necessary improvements can be made for optimal aerodynamic capabilities that improve fuel efficiency, reduce drag and improve performance in hazardous conditions.

History

Wind tunnels have been used since the beginning of the 20th century, for example by the Wright Brothers. As the need for more advanced aeronautic research became apparent, the National Aeronautics and Space Administration (NASA) began operating more advanced wind tunnels beginning in 1921. According to NASA's Aeronautical Facilities Catalogue, NASA currently operates 23 wind tunnels in Virginia, 12 in California, six in Ohio and one in Alabama. Other nations with wind tunnels include: the United Kingdom, France, Germany, Japan, the Netherlands and Canada.

Structure

Wind tunnels began small, as boxes with fans that blew the air through the tube while the object was suspended from the top. The results were not read by computers, but by human eyes. Currently, wind tunnel walls are round and are as sheer as possible, with windows for viewing while computers record data. Depending on the size, the air is blown in or sucked out with a series of fans while air vanes regulate airflow.

Function

Wind tunnels record the pressure of the air on the object. Air velocity is monitored in a test section of the object. Substances such as smoke are introduced to the wind tunnel and show researchers what path air follows around the object; strings can show researchers which way the wind is blowing. Devices planted on the object can record the pressure exerted on the object.

Types

Wind tunnels are designed for different purposes. Some record data from below the speed of sound, while others record data at five times the speed of sound. Some wind tunnels have a more viscous atmosphere, depending on the craft being tested. Size and shape are also variants. Wind tunnels for testing objects are horizontal, but those used by skydivers are vertical.

NASA's Current Wind Tunnels

Langley Research Center houses some of NASA's most advanced wind tunnels. One is able to simulate flight conditions at 1.2 times the speed of sound accurately; another tests at speeds up to Mach 7. Langley scientists are also experimenting with magnet suspension. Lewis Research Center studies aircraft propulsion systems, testing aircraft with their engines turned on, takeoffs and landings. They also conduct research on hazardous flying conditions, such as ice storms. Ames Research Center houses the world's largest wind tunnel, designed specifically for testing enormous aircraft. It operates with six 15-bladed fans, each with the diameter of a four-story building.

References

• NASA's Wind Tunnel Fact Sheet
• The Wind Tunnels of NASA

Resources

• Bodyflight Bedford
• Aerodynamic Study of the Wright Brothers' Wind Tunnel