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Student Reading
Wind Tunnels
Sometimes scientists create a model to help them explain how
or why something works the way it does.
You may have seen model airplanes. These model airplanes are smaller
than the real thing, and while the outside might look like the real thing,
the inside does not. Many models are scale models. This means that
every part of the airplane is made smaller by the same amount. Thus a
scale model is an exact copy of the real thing - only smaller!
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A scale model can be used to test a researcher's hypothesis
in a safe and controlled way. In aeronautics, researchers and engineers
use models to design and modify airplanes.
Aeronautical researchers can make a scale model and mount it in
a wind tunnel. A wind tunnel is a tube or tunnel through
which air is blown. So, instead of an airplane flying through the
air, a scale model of the airplane is mounted in a wind tunnel and
air is blown around it.
Some wind tunnels are very large and can hold models that are
the size of the real airplane. Some wind tunnels are very small
and can only hold very tiny scale models of the airplane, or maybe
a scale model of a part of the airplane. Some very small wind tunnels
can only blow air only at very high speeds (over 3,000 miles per
hour), while some of the largest tunnels blow air at less than 150
miles per hour. This may sound slow, but this is near takeoff and
landing speeds for many airplanes. So, these big wind tunnels are
very useful.
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A model of an F-18 in the 80x120-foot test section
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Over the years, NASA's Ames Research Center has operated over 20 wind
tunnels of varying sizes and purposes. Today, however, three major tunnels
are used at Ames to support civilian and military model tests:
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1. The National Full-Scale Aerodynamics Complex (NFAC) contains
the 80x120-Foot Wind Tunnel and the 40x80-Foot Wind Tunnel. In wind
tunnels, Ò80x120-Foot" and "40x80-Foot" indicates dimensions
of the spaces in which the aircraft are tested. Both do large-scale
or full-scale testing of aircraft and rotorcraft. The 80x120 tunnel
will be used to test the Wright Flyer replica.
2. The Unitary Plan Wind Tunnel has tested many models of commercial
vehicles and fighter planes, as well as spacecraft from the Mercury,
Gemini and Apollo programs and the Space Shuttle. The tunnel contains
separate test sections for transonic and supersonic flight testing.
In 1985, the facility was named a National Historic Landmark by
the National Park Service because of "its significant associations
with the development of the American Space Program."
3. The 12-Foot Pressure Wind Tunnel collects test data to support
the development of high-lift systems for commercial transports and
military aircraft and tests high angle-of-attack of maneuvering
aircraft. Increasing the air pressure inside the tunnel makes the
airflow around a small-scale model closer to the flow experienced
on a full-size aircraft.
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80x120 Wind Tunnel at NASA Ames Research Center
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Engineers place instruments on the scale model and in the wind tunnel
to take measurements while the wind is blowing. They measure the forces
on the model and the pressures. All the measurements are collected and
analyzed so that the researcher's hypothesis may be proved or disproved.
In September 1992, the Los Angeles Section of the American Institute
of Aeronautics and Astronautics (AIAA) approached the managers of the
wind tunnels at NASA Ames to discuss a proposal for a test of their full-scale
replica of the 1903 Wright Flyer. Although there have been some delays
due to the schedules of other customers using the tunnel, as well as some
recent construction in the tunnel, the Flyer is now on the 80x120-Foot
Wind Tunnel calendar for 1999. The test will support two main goals:
- It will provide aerodynamic data about the first successful, piloted
airplane in history
- the information will be used by AIAA to build a new, safe, near-replica
to be flown at Kitty Hawk, North Carolina on December 17, 2003 in a
centennial celebration of the birth of powered flight.
1903 Wright Flyer
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