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.