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Propulsion Wind Tunnel Facility

Arnold Engineering Development Center Arnold Air Force Base, Tenn. 37389

An Air Force Materiel Command Test Facility

Arnold Engineering Development Center, (AEDC) located in southern Middle Tennessee, is the nation’s larg-est aerospace ground test facility com-plex. The complex includes 58 aerody-namic and propulsion wind tunnels,rocket and turbine engine test cells,space environmental chambers, arc heat-ers, ballistic ranges and other special-ized test units. Twenty-seven of the test units have capabilities unmatched in the United States and 14 have capabilities unmatched in the world. Using its ground test facilities, AEDC supports propulsion,aerodynamic, reentry, trans-atmospheric and space-flight systems testing and space-flight systems testing.Terms to Know

M ach number —a ratio unit of speed,

Devoted to aerodynamic and propul-sion integration testing of large-scale air-craft models, PWT is used to provide AEDC’s customers with complete test-ing and analysis capability. In some cases, the propulsion systems and in-lets are tested simultaneously to make sure they are aerodynamically designed to provide adequate airflow to the engines.Other tests involve store separation in-vestigations—making sure bombs, mis-siles or other externally carried stores separate cleanly from the parent aircraft when released.

The facility boasts some of the most

Propulsion Wind Tunnel Facility

Photo no. 02-01006

Photo no. D0410455

The Lockheed M artin F-35 Lightning II Joint Strike Fighter in the 16-foot

transonic wind tunnel.

named after Austrian philosopher and physicist Ernst Mach (1838-1916), used when talking about aircraft or missiles;defined as a ratio of the speed of an air-craft to the speed of sound in the undis-turbed medium (air) through which the body is traveling. Mach 1 is approximately equal to 717 miles/hour at sea level.Transonic —sub-sonic to low super-sonic speed S u p e r s o n i c —speeds above Mach 1.

S t o r e s —f u e l tanks, bombs, ex-ternal pods or mis-siles that are car-ried by an aircraft.

AEDC Wind Tunnels

AEDC’s wind tunnels include the Pro-pulsion Wind Tunnels (16T , 16S and 4T),the von Karman Gas Dynamics Facility (VKF) Supersonic and Hypersonic Wind Tunnels A/B/C. AEDC also operates two remote facilities Hypervelocity Tunnel 9Wind Tunnel, located in White Oak,Maryland, and the National Full-Scale Aerodynamic Facility (NFAC) at Moffett Field, Calif. Individual fact sheets are avail-able for further information on Hypervelocity Tunnel 9 and VKF Super-sonic and Hypersonic Wind Tunnels.

Propulsion Wind Tunnel

Facility

The PWT facility is composed of the 16-foot transonic (16T), 16-foot super-sonic (16S) and the aerodynamic 4-foot transonic (4T) wind tunnels. The 16-foot supersonic wind tunnel is currently in in-

active status.

AEDC aerodynamic test of the Space Shuttle with solid rocket boosters and external fuel tank in the 16-foot transonic wind tunnel conducted in support of NASA’s return to flight. Inset image is a pressure sensitive paint image of the shuttle test.

Photo no. D0412265

AEDC

powerful electric motors ever built—tall as a two-story house and as heavy as a railroad locomotive. Four motors—two at 83,000 horsepower each and a smaller pair rated at 60,000 horsepower each—drive five compressors that can generate airflow in excess of 2,000 miles per hour in PWT’s transonic and supersonic tun-nels. Both 83,000-hp motors stand 21-1/2 feet high and weigh 225 tons with 31miles of copper wire used in the motor windings.

PWT was designated an International Historical Mechanical Engineering Land-mark in 1989 by the American Society of Mechanical Engineers.

16T and 16S

The facility has two 16-foot-square, 40-foot long test sections, closed-circuit wind tunnels, one transonic (16T) and one su-personic (16S).

The 16T facility is capable of being op-erated at Mach numbers from 0.06 to 1.60.

The inactive 16S facility is capable of operation from Mach numbers from 1.60to 4.0.

Both tunnels can be used for conven-tional aerodynamic tests and for com-bined aerodynamic/propulsion systems tests. Pressure of the airflow through the test sections can be varied to simulate altitude conditions from sea level to about 150,000 feet.

The large tunnel size also allows for full-scale missile installations to test en-gine performance and airframe aerody-namics. Rocket propulsion systems and problems associated with their external

aerodynamics are also investigated. Because of their large size, the PWT 16-foot tunnels are adaptable to the testing of parachutes or other https://www.sodocs.net/doc/7b16558000.html,ing specially built inanimate dummies,measurements have been made of the aero-dynamic forces acting on the human body during emergency

ejection from an air-craft traveling at speeds up to 900mph.Both large tun-nels have inter-changeable test sections, allowing preparations for one test to be made while an-other is being run in the tunnel. To eliminate swirling and turbulence,which could affect test results, the airflow is guided smoothly around the right-angle turns of the closed-circuit tun-nels by giant turn-ing vanes that re-semble huge, ver-tical venetian blinds. A flexible

nozzle regulates the velocity of the air-flow as it enters the test section.

Some of the features of the 16-foot tun-nels include a moveable support system called a strut. The strut is attached to the floor of the wind tunnel’s test sec-tion. The tunnels are also equipped with a special movable support system, called a sting, for mounting additional models.To simulate change in flight attitudes or maneuvers, the support is yawed (moved side to side), rolled or pitched up or down.The 16-foot tunnels can be used to ex-amine the relationship between engine air inlets and the corresponding performance of and compatibility with the engine it-self. This is done to determine the most efficient air-induction system design or to study how varying the geometrical shape of an inlet or propulsion nozzle can affect the aerodynamics of the flight ve-hicle. Both tunnels also have a scaveng-ing system that removes combustion products when testing rocket motors or gas turbine (jet) engines.

4T

The four-foot aerodynamic wind tunnel (4T) is PWT’s versatile, mid-size test unit that has a 4-foot by 4-foot by 12.5-foot long test section. The transonic desig-nation indicates its primary utility is for testing from subsonic to low end super-sonic airspeeds. Its capability is roughly equivalent to an airspeed range from 160

to 1,600 miles per hour.

Photo no. D412350

Photo no. 0106402

A model of the Boeing 747X aircraft in

AEDC’s 16-foot transonic wind tunnel.

Photo no. 72-14F-15 Eagle full scale inlet and operating engine being tested in AEDC’s 16-foot supersonic wind tunnel The tests demonstrated the compatibility of the Pratt & Whitney F-100 jet engine with

the aircrafts variable geometry inlet.

An AEDC technician in the 16-foot transonic wind tunnel speaks through a microphone to control room personnel who are

operating a sting with a store for the Navy EA-18G Growler model to ensuring control operators do not damage the store or aircraft model during testing by exceeding “touch points” of contact between the components.

Store Separation Testing

At transonic speeds and at certain al-titudes or maneuver conditions, the aero-dynamic forces on an aircraft’s stores—bombs, missiles or drop tanks carried externally—separating from an aircraft may cause the store to veer upward when released and collide with the aircraft.In years past, bombs were carried and dropped out of bays, but as highthrust engines became available, the weapons could be shifted outside and carried in considerable numbers on pylons attached to the lower surface of the wings or car-ried in numbers in an internal weapons bay. Problems became evident when the aircraft speed became progressively faster.

The dynamics of clean store separa-tion—investigations of aerodynamic forces that can alter the planned trajec-tory of air-launched bombs or missiles—is explored in the 16- and 4-foot tunnels.The aircraft model is mounted upside down in the tunnel on a strut. The store model is mounted on a special moveable support system called a sting attached within the test section and positioned very close to the aircraft as it would be in flight.When the desired simulated flight con-ditions are established in the tunnel, the store model is “launched” from the par-ent aircraft model by activating a com-puter that controls movement of the sting-supported store as it traces the trajec-tory.

Information obtained in these tests is used to design new stores or to modify existing ones, or modify carriage and re-lease mechanisms to make sure they separate cleanly, do not damage the par-ent aircraft, and stay on the intended flight path in the proper attitude.

Captive Trajectory Support Testing

The Captive Trajectory Support (CTS) systems for the AEDC wind tunnels allows computer-controlled, six-degrees-of-free-dom positioning of a missile,bomb or any other store in close proximity to the aircraft model.Operational CTS systems exist in tunnels 4T and 16T. Applica-tions in the PWT transonic and supersonic test units consist of store separation and flow-field mapping.

Pressure Sensitive Paint

(PSP) Capability

AEDC became involved with the ever evolving technology of PSP in 1993. The technique uses a special paint and illu-mination source combined with an ex-tremely sensitive camera to obtain sur-face pressure data. PSP paint is applied to the model in two layers—a white un-dercoat and the PSP layer. The white undercoat provides a uniform reflective sur-face for the PSP layer. The illumination source excites the PSP layer, which fluo-resces with intensity inversely propor-tional to the surface pressure on the model.

In 1999, a Multi-View PSP data acqui-sition system was installed in 16T. PSP can determine the surface pressure at several hundred thousand locations on wind tunnel models while conventional in-strumentation is limited to several hun-dred pressure openings. Also, pressure orifices cannot be installed in some ar-

eas of the model, such as thin surfaces,limiting the measurement of the surface pressure. PSP measurements are only limited if there are areas of the model that cannot be seen by one of the cameras.

Computational Support to Test and Evaluation

AEDC provides a wide range of com-

putational support to the test and evalua-

Photo no. 09910035

Photo no. 97-03259

Photo no. 99082505

A pressure sensitive paint generated

image of the Global Hawk unmanned air vehicle.

A pressure sensitive paint computational generated image of the F-16 Fighting Falcon.

A computational image generated image of an Evolved Expendable Launch Vehicle (EELV) coated with pressure sensitive paint.

A model of the F-16 Fight Falcon aircraft in the 16-foot transonic wind tunnel with pressure sensitive

paint applied to its surface.

tion process that affects how the Army,Navy and Air Force develop new weap-ons systems. Calculations are used for several reasons, but one of the main rea-sons is to try and predict in advance what will happen during the test. Knowing this information allows test engineers to be better prepared for the test and to know beforehand of any problem areas. Another reason computations are used to support testing is to reduce the amount of testing that was once required. For example,certain types of testing requires the tun-nel to be run at many different settings (Mach number, temperatures, pressures,etc.), but the number of settings might be reduced if this information can instead be generated using computational simu-lation.

The center is continually updating and improving the way it conducts computa-tional studies because of several factors,such as improvements in computational techniques and improvements in comput-ers. AEDC operates one of the Depart-ment of Defense’s High Performance Computing Centers. AEDC also works with companies, universities and other govern-ment agencies (e.g., NASA) in partner-

ships and alliances be-cause much more can be accomplished working as a team than can be work-ing alone.

The combination of us-ing computations to-gether with the wind tun-nel results in a process known as Integrated T est and Evaluation (IT&E).Similar to people working as a team, much more can be accomplished using computations and the wind tunnel as a “team” than can be ac-complished by either

working by itself. Using the IT&E ap-proach allows AEDC customers to test more efficiently and with less risk. Per-forming pre-test predictions of the behav-ior of the test article in the tunnel allows

the test plan to be optimized and allows more usable information to be processed thus increasing the test product value by saving the customer time and money as well as reducing risk to the program.

21st Century Testing Technology An Air Force-funded $80-million PWT

upgrade program, completed in 2005, pro-vides AEDC with 21st century testing

technology. K nown as the Propulsion

Wind Tunnel Sustainment Program, the

program fully automated the PWT test

facility. Improvements from the program include installation of all new data acqui-sition and control systems in PWT’s 16-foot transonic wind tunnel, model instal-lation building and operation plants.

Propulsion Wind Tunnels

Background

Planning for the Propulsion Wind Tun-nels began in January 1950, when the Air Force Research and Development

Board on Facilities met with representa-Photo no. 0040009

The F-22A Raptor, the Air Force’s new air dominance fighter during store separation testing in AEDC’s 16-foot transonic wind tunnel.Photo no. 99-071804The B-1B Lancer bomber and the Joint Air to Surface Standoff M unition

undergoing store separation testing in the 16-foot transonic wind tunnel.

tives of aircraft propulsion companies and agreed that industry needed a supersonic propulsion wind tunnel with a 15-foot-di-ameter test section.

By December 1951, the commanding general at AEDC had approved a proposal for design, construction and operation of a scale model of the PWT transonic cir-cuit. The initial test facility was a one-foot cross-section prototype transonic tun-nel, and the first test was performed June 1953 on a 0.03-scale model of the

Bomarc missile for the Boeing Company.

In 1956, the transonic circuit, with its

16-foot test section, underwent its first

powered operation preliminary to calibra-tion.

The entire PWT complex was accepted

by the Air Force in January 1961. The

approximate cost of the 39 contracts to

construct the facility was $78.7 million.

PWT Aerial

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