Wind Tunnels In this report I will talk about the wind tunnel. I will described what theyare used for. The different types of wind tunnels from the slow speed subsonicto the high speed hypersonic tunnels. I will also give A few examples of thewind tunnels used today.
The wind tunnel is a device used by many people, from High school studentsto NASA engineers. The wind tunnel is a device used to test planes to see howwell it will do under certain conditions. The plane maybe as big as a full size747 or as small as a match. To understand how a wind tunnel is used to help inthe 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, androckets on the ground under pre-set conditions. With a wind tunnel you can chosethe air speed, pressure, altitude and temperature to name a few things. A windtunnel is usually has a tube like appearance with which wind is produced by alarge fan to flow over what they are testing (plane, missiles, rockets, etc.
)ora model of it. The object in the wind tunnel is fixed and placed in the testsection of the tunnel and instruments are placed on the model to record theaerodynamic 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 theamount of speed they can produce. The subsonic has a speed lower then the speedof 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 thehypersonic (Mach39.5) which has a speed of more then 30,000 miles per hour.Wind Tunnel TestThere are basically two types of wind tunnel test which are staticstability and the pressure test.
With these two test you can determine theaerodynamic characteristics of the aircraft. The static stability test themeasures the forces moments due to the external characteristic. These forcesinclude axial, side and normal force, rolling, pitching and yawing moment. Thisforces are found by using a strain gauge which is located on the externalportion of the plane. It measures the external flow fields. Then the shadowgraphis used to show the shock waves and flow fields at a certain speed or angle ofattack.
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 testobject. This is done by placing taps over the surface. The taps are thenconnected to transducers that read the local pressures. With this informationthey the can balance out the plane.
Then the static stability and the pressuretest data are combined to find the distributed loads.Wind Tunnels Used TodayWind 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 SpaceAdministration or NASA, at moffet Field, California. This wind tunnel at Amescan accommodate a Full-size aircraft with a wingspan of 22m (72ft).
They alsohave a hypervelocity tunnel at Ames that can create air velocities of up to30,000 mph (48,000 km/h) for one second. This high speed is able to be done byplacing a small model of the spacecraft in a device that produces an explosivecharge into the tunnel in one direction, while this is going on there is anotherexplosive charge that simultaneously pushes gas into the tunnel from the otherdirection. There is also a wind tunnel at the Lewis Flight Propulsion Laboratoryalso own by NASA in Cleveland, Ohio, can test full-size jet engines at airvelocities of up to 2,400mph (3860km/h) and at altitudes of up to 100,000ft(30,500m).Benefits of the Wind TunnelThere are many benefits that one can gain in using a wind tunnel. Sincedesigning an airplane is a long and complicated process and an expensive one aswell.
With the wind tunnel you can build models and test them at a fraction ofthe price compared to making the real thing. When designing an airplane one hasto take into account the public safety and still be able to keep the design inmind to do what it is designed to do. With a wind tunnel you can design and testwhat you make before you make it.With a wind tunnel you can also solve problems that already exist. Oneexample of this is when the first jet engine propelled aircraft’s where producedin the 40’s . The problem occurred when the jet planes released there missilesthat where on the external part of the plane, the missiles had a tendency tomove up when released causing a collision with the plane resulting in death ofthe pilot .With the wind tunnel the were able to solve this problem with out thelost of any more lives.
On February 1, 1956 wind tunnels were so important that the Army formedthe ABMA at Redstone Arsenal in Huntsville, Alabama from army missile programassets. This program was made to support for on going research and developmentprojects for the army ballistic missile program in this program they made a14inc wind tunnel to test the missiles. Early test were done to determine theaerodynamics of the Jupiter IRBM (Intermediate Range Ballistic Missile)and itsnose cone. The Jupiter C missile was one of the first Launch Vehicles tested inthe wind tunnel. The Jupiter C was a modified Redstone rocket made of nose conere-entry testing. A modified Jupiter C the Juno 1, launched America’s firstsatellite, the explorer 1 into orbit. Soon after this the ABMA wind tunnel wentto NASA.
The wind tunnel played a vital role in the exploration of space. Thewind tunnel played a major role in the Saturn V, the first rocket that put thefirst man on the moon(Apollo mission) to the current Space Shuttle LaunchVehicle. The tunnel mission changed from testing medium to long range missilesto supporting America’sRace Into Space. NASA increased the payload of theoriginal 10lb satellite(explorer 1 ) to a man in a capsule(project Mercury). Tothe Apollo Project.
The Saturn family of launch vehicles spent hundreds of hoursin the wind tunnel. There were various configurations that were tried to findthe best result. At first they were going to make a fully reusable shuttle butthat idea cost to much and was ruled out due to there budget. With the budget inmind the current space shuttle started to be formed. But it still took manyyears in a wind tunnel before the final design of the Orbiter, External Tank andSolid Rocket Boosters final took there shape as the one we know of today.
Evenafter the space shuttle took flight they were still being tested to increaseperformance. Test were done to determine the cause of tile damage. As theshuttle program continued to progress at a rapid pace it came to a stand stillwhen the Challenger Accident occurred.
After the accident the 14in wind tunnelwas immediately put into use. to analyze what had occurred. These test verifiedwhat happen to the SRB leak and the rupture of the aft external tank STA 2058ring frame. The data was used to determine the trajectory and controlreconstruction. With all of this information they got from this they are tryingto develop a way to abort scenarios involving orbiter separation duringtransonic flight. All of these configuration were done to the scale model thatis .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 windtunnel the cost of designing an aircraft and testing an aircraft has beenreduced, And most important lives have been saved. With out the wind tunnelthere would be no way for us to know what will happen before it happens.