Wind Tunnels


In this report I will talk about the wind tunnel. I will described what they
are used for. The different types of wind tunnels from the slow speed subsonic
to the high speed hypersonic tunnels. I will also give A few examples of the
wind tunnels used today.
The wind tunnel is a device used by many people, from High school students
to NASA engineers. The wind tunnel is a device used to test planes to see how
well it will do under certain conditions. The plane maybe as big as a full size
747 or as small as a match. To understand how a wind tunnel is used to help in
the designing process you have to know how a wind tunnel works.

How Wind Tunnels Work

A wind tunnel is a machine used to fly aircraft's, missiles, engines, and
rockets on the ground under pre-set conditions. With a wind tunnel you can chose
the air speed, pressure, altitude and temperature to name a few things. A wind
tunnel is usually has a tube like appearance with which wind is produced by a
large fan to flow over what they are testing (plane, missiles, rockets, etc.)or
a model of it. The object in the wind tunnel is fixed and placed in the test
section of the tunnel and instruments are placed on the model to record the
aerodynamic forces acting on the model.

Types of Wind Tunnels

There are four basic types of wind tunnels. Which are low subsonic,
transonic, supersonic, and hypersonic. The wind tunnels are classified by the
amount of speed they can produce. The subsonic has a speed lower then the speed
of sound. The transonic has a speed which is about equal to the speed of sound
(Mach 1 760 miles per hour at sea level). . The supersonic (Mach 2.75 to 4.96)
has a speed of about five times the speed of sound And the fasts of them all the
hypersonic (Mach39.5) which has a speed of more then 30,000 miles per hour.

Wind Tunnel Test

There are basically two types of wind tunnel test which are static
stability and the pressure test. With these two test you can determine the
aerodynamic characteristics of the aircraft. The static stability test the
measures the forces moments due to the external characteristic. These forces
include axial, side and normal force, rolling, pitching and yawing moment. This
forces are found by using a strain gauge which is located on the external
portion of the plane. It measures the external flow fields. Then the shadowgraph
is used to show the shock waves and flow fields at a certain speed or angle of
attack. There is also the oil flow which shows you the surface flow pattern.
The pressure test is used to provide the pressures acting on the test
object. This is done by placing taps over the surface. The taps are then
connected to transducers that read the local pressures. With this information
they the can balance out the plane. Then the static stability and the pressure
test data are combined to find the distributed loads.

Wind Tunnels Used Today

Wind tunnel vary in size from a few inches to 12m by 24m (40ft by 80ft)
located at the Ames Research Center of the National Aeronautics and Space
Administration or NASA, at moffet Field, California. This wind tunnel at Ames
can accommodate a Full-size aircraft with a wingspan of 22m (72ft). They also
have a hypervelocity tunnel at Ames that can create air velocities of up to
30,000 mph (48,000 km/h) for one second. This high speed is able to be done by
placing a small model of the spacecraft in a device that produces an explosive
charge into the tunnel in one direction, while this is going on there is another
explosive charge that simultaneously pushes gas into the tunnel from the other
direction. There is also a wind tunnel at the Lewis Flight Propulsion Laboratory
also own by NASA in Cleveland, Ohio, can test full-size jet engines at air
velocities of up to 2,400mph (3860km/h) and at altitudes of up to 100,000ft
(30,500m).

Benefits of the Wind Tunnel

There are many benefits that one can gain in using a wind tunnel. Since
designing an airplane is a long and complicated process and an expensive one as
well. With the wind tunnel you can build models and test them at a fraction of
the price compared to making the real thing. When designing an airplane one has
to take into account the public safety and still be able to