Wind Tunnels Essay, Research Paper
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 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.