Wind Tunnel

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 keep the
design in mind to do what it is designed to do. With a wind tunnel you can design and test what
you make before you make it.
With a wind tunnel you can also solve problems that already exist. One example of this is
when the first jet engine propelled aircraft’s where produced in the 40’s . The problem occurred
when the jet planes released there missiles that where on the external part of the plane, the
missiles had a tendency to move up when released causing a collision with the plane resulting in
death of the pilot .With the wind tunnel the were able to solve this problem with out the lost of
any more lives.
On February 1, 1956 wind tunnels were so important that the Army formed the ABMA at
Redstone Arsenal in Huntsville, Alabama from army missile program assets. This program was
made to support for on going research and development projects for the army ballistic missile
program in this program they made a 14inc wind tunnel to test the missiles.
Early test were done to determine the aerodynamics of the Jupiter IRBM (Intermediate
Range Ballistic Missile)and its nose cone. The Jupiter C missile was one of the first Launch
Vehicles tested in the wind tunnel. The Jupiter C was a modified Redstone rocket made of nose
cone re-entry testing. A modified Jupiter C the Juno 1, launched America’s first satellite, the
explorer 1 into orbit. Soon after this the ABMA wind tunnel went to NASA. The wind tunnel
played a vital role in the exploration of space. The wind tunnel played a major role in the Saturn
V, the first rocket that put the first man on the moon(Apollo mission) to the current Space Shuttle
Launch Vehicle. The tunnel mission changed from testing medium to long range missiles to
supporting America’s “Race Into Space”. NASA increased the payload of the original 10lb
satellite(explorer 1 ) to a man in a capsule(project Mercury). To the Apollo Project. The Saturn
family of launch vehicles spent hundreds of hours in the wind tunnel. There were various
configurations that were tried to find the best result. At first they were going to make a fully
reusable shuttle but that idea cost to much and was ruled out due to there budget. With the
budget in mind the current space shuttle started to be formed. But it still took many years in a
wind tunnel before the final design of the Orbiter, External Tank and Solid Rocket Boosters final
took there shape as the one we know of today. Even after the space shuttle took flight they were
still being tested to increase performance. Test were done to determine the cause of tile damage.
As the shuttle program continued to progress at a rapid pace it came to a stand still when the
Challenger Accident occurred. After the accident the 14in wind tunnel was immediately put into
use. to analyze what had occurred. These test verified what happen to the SRB leak and the
rupture of the aft external tank STA 2058 ring frame. The data was used to determine the
trajectory and control reconstruction. With all of this information they got from this they are
trying to develop a way to abort scenarios involving orbiter separation during transonic flight. All
of these configuration were done to the scale model that is .004 of the real shuttle.
This is just a few applications of the wind tunnel. There are many more things that they
can do. With the invention of the wind tunnel the cost of designing an aircraft and testing an
aircraft has been reduced, And most important lives have been saved. With out the wind tunnel
there would be no way for us to know what will happen before it happens.


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