Wind tunnel
Overview
 
A wind tunnel is a research tool used in aerodynamic
Aerodynamics
Aerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object. Aerodynamics is a subfield of fluid dynamics and gas dynamics, with much theory shared between them. Aerodynamics is often used synonymously with gas dynamics, with...

 research to study the effects of air moving past solid objects.
Wind tunnels were first proposed as a means of studying vehicles (primarily airplanes) in free flight. The wind tunnel was envisioned as a means of reversing the usual paradigm: instead of the air's standing still and the aircraft moving at speed through it, the same effect would be obtained if the aircraft stood still and the air moved at speed past it.
Encyclopedia
A wind tunnel is a research tool used in aerodynamic
Aerodynamics
Aerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object. Aerodynamics is a subfield of fluid dynamics and gas dynamics, with much theory shared between them. Aerodynamics is often used synonymously with gas dynamics, with...

 research to study the effects of air moving past solid objects.

Theory of operation

Wind tunnels were first proposed as a means of studying vehicles (primarily airplanes) in free flight. The wind tunnel was envisioned as a means of reversing the usual paradigm: instead of the air's standing still and the aircraft moving at speed through it, the same effect would be obtained if the aircraft stood still and the air moved at speed past it. In that way a stationary observer could study the aircraft in action, and could measure the aerodynamic forces being imposed on the aircraft.

Later on, wind tunnel study came into its own: the effects of wind on manmade structures or objects needed to be studied when buildings became tall enough to present large surfaces to the wind, and the resulting forces had to be resisted by the building's internal structure. Determining such forces was required before building code
Building code
A building code, or building control, is a set of rules that specify the minimum acceptable level of safety for constructed objects such as buildings and nonbuilding structures. The main purpose of building codes are to protect public health, safety and general welfare as they relate to the...

s could specify the required strength of such buildings.

Still later, wind-tunnel testing was applied to automobiles, not so much to determine aerodynamic forces per se but more to determine ways to reduce the power required to move the vehicle on roadways at a given speed. In these studies, the interaction between the road and the vehicle plays a significant role, and this interaction must be taken into consideration when interpreting the test results. In an actual situation the roadway is moving relative to the vehicle but the air is stationary relative to the roadway, but in the wind tunnel the air is moving relative to the roadway, while the roadway is stationary relative to the test vehicle. Some automotive-test wind tunnels have incorporated moving belts under the test vehicle in an effort to approximate the actual condition.

Measurement of aerodynamic forces

Ways that air velocity and pressures are measured in wind tunnels:
  • air velocity through the test section is determined by Bernoulli's principle
    Bernoulli's principle
    In fluid dynamics, Bernoulli's principle states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy...

    . Measurement of the dynamic pressure, the static pressure
    Static pressure
    In fluid mechanics the term static pressure has several uses:* In the design and operation of aircraft, static pressure is the air pressure in the aircraft’s static pressure system....

    , and (for compressible flow
    Compressible flow
    Compressible flow is the area of fluid mechanics that deals with fluids in which the fluid density varies significantly in response to a change in pressure. Compressibility effects are typically considered significant if the Mach number of the flow exceeds 0.3, or if the fluid undergoes very large...

     only) the temperature rise in the airflow
  • direction of airflow around a model can be determined by tufts of yarn attached to the aerodynamic surfaces
  • direction of airflow approaching an aerodynamic surface can be visualized by mounting threads in the airflow ahead of and aft of the test model
  • dye, smoke, or bubbles of liquid can be introduced into the airflow upstream of the test model, and their path around the model can be photographed (see particle image velocimetry
    Particle image velocimetry
    Particle image velocimetry is an optical method of flow visualization used in education and research. It is used to obtain instantaneous velocity measurements and related properties in fluids...

    )
  • pressures on the test model are usually measured with beam balances, connected to the test model with beams or strings or cables
  • pressure distributions across the test model have historically been measured by drilling many small holes along the airflow path, and using multi-tube manometers to measure the pressure at each hole
  • pressure distributions can more conveniently be measured by the use of pressure-sensitive paint
    Pressure-sensitive paint
    Pressure-sensitive paint is a method for measuring air pressure, usually in aerodynamic settings. It is paint which fluoresces in differing intensities depending on the external air pressure being applied to its surface.-Where it is used:...

    , in which higher local pressure is indicated by lowered fluorescence of the paint at that point
  • pressure distributions can also be conveniently measured by the use of pressure-sensitive pressure belts, a recent development in which multiple ultra-miniaturized pressure sensor modules are integrated into a flexible strip. The strip is attached to the aerodynamic surface with tape, and it sends signals depicting the pressure distribution along its surface.
  • pressure distributions on a test model can also be determined by performing a wake survey, in which either a single pitot tube
    Pitot tube
    A pitot tube is a pressure measurement instrument used to measure fluid flow velocity. The pitot tube was invented by the French engineer Henri Pitot Ulo in the early 18th century and was modified to its modern form in the mid-19th century by French scientist Henry Darcy...

     is used to obtain multiple readings downstream of the test model, or a multiple-tube manometer is mounted downstream and all its readings are taken (often by photograph).

Origins

English military engineer and mathematician Benjamin Robins
Benjamin Robins
Benjamin Robins was a pioneering English scientist, Newtonian mathematician, and military engineer.He wrote an influential treatise on gunnery, for the first time introducing Newtonian science to military men, was an early enthusiast for rifled gun barrels, and his work had substantive influence...

 (1707–1751) invented a whirling arm apparatus to determine drag and did some of the first experiments in aviation theory.

Sir George Cayley (1773–1857) also used a whirling arm to measure the drag and lift of various airfoils. His whirling arm was 5 feet (1.5 m) long and attained top speeds between 10 and 20 feet per second.

However, the whirling arm does not produce a reliable flow of air impacting the test shape at a normal incidence. Centrifugal forces and the fact that the object is moving in its own wake mean that detailed examination of the airflow is difficult. Francis Herbert Wenham
Francis Herbert Wenham
Francis Herbert Wenham was a British marine engineer who studied the problem of manned flight and wrote a perceptive and influential academic paper which he presented to the first meeting of the Royal Aeronautical Society in London in 1866.Wenham's report, "Aerial Locomotion," was published in the...

 (1824–1908), a Council Member of the Aeronautical Society of Great Britain, addressed these issues by inventing, designing and operating the first enclosed wind tunnel in 1871. Once this breakthrough had been achieved, detailed technical data was rapidly extracted by the use of this tool. Wenham and his colleague Browning are credited with many fundamental discoveries, including the measurement of l/d ratios, and the revelation of the beneficial effects of a high aspect ratio
Aspect ratio (wing)
In aerodynamics, the aspect ratio of a wing is essentially the ratio of its length to its breadth . A high aspect ratio indicates long, narrow wings, whereas a low aspect ratio indicates short, stubby wings....

.

Carl Rickard Nyberg used a wind tunnel when designing his Flugan
Flugan
Flugan was an early aeroplane designed and built by Carl Richard Nyberg outside his home in Lidingö, Sweden. Construction started in 1897 and he kept working on it until 1922. The craft only managed a few short jumps and Nyberg was often ridiculed, however several of his innovations are still in use...

 from 1897 and onwards.

In a classic set of experiments, the Englishman Osborne Reynolds
Osborne Reynolds
Osborne Reynolds FRS was a prominent innovator in the understanding of fluid dynamics. Separately, his studies of heat transfer between solids and fluids brought improvements in boiler and condenser design.-Life:...

 (1842–1912) of the University of Manchester
University of Manchester
The University of Manchester is a public research university located in Manchester, United Kingdom. It is a "red brick" university and a member of the Russell Group of research-intensive British universities and the N8 Group...

 demonstrated that the airflow pattern over a scale model would be the same for the full-scale vehicle if a certain flow parameter were the same in both cases. This factor, now known as the Reynolds Number, is a basic parameter in the description of all fluid-flow situations, including the shapes of flow patterns, the ease of heat transfer, and the onset of turbulence. This comprises the central scientific justification for the use of models in wind tunnels to simulate real-life phenomena. However, there are limitations on conditions in which dynamic similarity is based upon the Reynolds number alone.
The Wright brothers
Wright brothers
The Wright brothers, Orville and Wilbur , were two Americans credited with inventing and building the world's first successful airplane and making the first controlled, powered and sustained heavier-than-air human flight, on December 17, 1903...

' use of a simple wind tunnel in 1901 to study the effects of airflow over various shapes while developing their Wright Flyer
Wright Flyer
The Wright Flyer was the first powered aircraft, designed and built by the Wright brothers. They flew it four times on December 17, 1903 near the Kill Devil Hills, about four miles south of Kitty Hawk, North Carolina, U.S.The U.S...

 was in some ways revolutionary. It can be seen from the above, however, that they were simply using the accepted technology of the day, though this was not yet a common technology in America.

Subsequent use of wind tunnels proliferated as the science of aerodynamics and discipline of aeronautical engineering were established and air travel and power were developed.

The US Navy in 1916 built one of the largest wind tunnels in the world at that time at the Washington Navy Yard. The inlet was almost 11 feet (3.4 m) in diameter and the discharge part was 7 feet (2.1 m) in diameter. A 500 hp electric motor drove the paddle type fan blades.

Until World War Two, the world's largest wind tunnel was built in 1929 and located in a suburb of Paris, Chalais-Meudon, France. It was designed to test full size aircraft and had six large fans driven by high powered electric motors.

World War Two

In 1941 the US constructed one of the largest wind tunnels at that time at Wright Field in Dayton, Ohio. This wind tunnel starts at 45 feet (13.7 m) and narrows to 20 feet (6.1 m) in diameter. Two 40 feet (12.2 m) fans were driven by a 40,000hp electric motor. Large scale aircraft models could be tested at air speeds of 400 mph (643.7 km/h).

The wind tunnel used by German scientists at Peenemünde
Peenemünde
The Peenemünde Army Research Center was founded in 1937 as one of five military proving grounds under the Army Weapons Office ....

 prior to and during WWII
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 is an interesting example of the difficulties associated with extending the useful range of large wind tunnels. It used some large natural caves which were increased in size by excavation and then sealed to store large volumes of air which could then be routed through the wind tunnels. This innovative approach allowed lab research in high-speed regimes and greatly accelerated the rate of advance of Germany's aeronautical engineering efforts. By the end of the war, Germany had at least three different supersonic wind tunnels, with one capable of Mach 4.4 (heated) airflows.

By the end of World War Two, the US had built eight new wind tunnels, including the largest one in the world at Moffett Field near Sunnyvale, California, which was designed to test full size aircraft at speeds of less than 250mph.

Post World War Two

Later research into airflows near or above the speed of sound used a related approach. Metal pressure chambers were used to store high-pressure air which was then accelerated through a nozzle
De Laval nozzle
A de Laval nozzle is a tube that is pinched in the middle, making a carefully balanced, asymmetric hourglass-shape...

 designed to provide supersonic flow. The observation or instrumentation chamber ("test section") was then placed at the proper location in the throat or nozzle for the desired airspeed.

For limited applications, Computational fluid dynamics
Computational fluid dynamics
Computational fluid dynamics, usually abbreviated as CFD, is a branch of fluid mechanics that uses numerical methods and algorithms to solve and analyze problems that involve fluid flows. Computers are used to perform the calculations required to simulate the interaction of liquids and gases with...

 (CFD) can augment or possibly replace the use of wind tunnels. For example, the experimental rocket plane SpaceShipOne was designed without any use of wind tunnels. However, on one test, flight threads were attached to the surface of the wings, performing a wind tunnel type of test during an actual flight in order to refine the computational model. It should be noted that, for situations where external turbulent flow is present, CFD is not practical due to limitations in present day computing resources. For example, an area that is still much too complex for the use of CFD is determining the effects of flow on and around structures, bridges, terrain, etc.

The most effective way to simulative external turbulent flow is through the use of a boundary layer wind tunnel.

There are many applications for boundary layer wind tunnel modeling. For example, understanding the impact of wind on high-rise buildings, factories, bridges, etc. can help building designers construct a structure that stands up to wind effects in the most efficient manner possible. Another significant application for boundary layer wind tunnel modeling is for understanding exhaust gas dispersion patterns for hospitals, laboratories, and other emitting sources. Other examples of boundary layer wind tunnel applications are assessments of pedestrian comfort and snow drifting. Wind tunnel modeling is accepted as a method for aiding in Green building
Green building
Green building refers to a structure and using process that is environmentally responsible and resource-efficient throughout a building's life-cycle: from siting to design, construction, operation, maintenance, renovation, and demolition...

 design. For instance, the use of boundary layer wind tunnel modeling can be used as a credit for Leadership in Energy and Environmental Design
Leadership in Energy and Environmental Design
Leadership in Energy and Environmental Design consists of a suite of rating systems for the design, construction and operation of high performance green buildings, homes and neighborhoods....

 (LEED) certification through the U.S. Green Building Council.

Wind tunnel tests in a boundary layer wind tunnel allow for the natural drag of the Earth's surface to be simulated. For accuracy, it is important to simulate the mean wind speed profile and turbulence effects within the atmospheric boundary layer. Most codes and standards recognize that wind tunnel testing can produce reliable information for designers, especially when their projects are in complex terrain or on exposed sites.

In the USA many wind tunnels have been decommissioned in the last 20 years, including some historic facilities. Pressure is brought to bear on remaining wind tunnels due to declining or erratic usage, high electricity costs, and in some cases the high value of the real estate upon which the facility sits. On the other hand CFD validation still requires wind-tunnel data, and this is likely to be the case for the foreseeable future. Studies have been conducted and others are under way to assess future military and commercial wind tunnel needs, but the outcome remains uncertain. More recently an increasing use of jet-powered, instrumented unmanned vehicles ["research drones"] have replaced some of the traditional uses of wind tunnels.

How it works

Air is blown or sucked through a duct equipped with a viewing port and instrumentation where models
Model (physical)
A physical model is a smaller or larger physical copy of an object...

 or geometrical shapes are mounted for study. Typically the air is moved through the tunnel using a series of fans. For very large wind tunnels several meters in diameter, a single large fan is not practical, and so instead an array of multiple fans are used in parallel to provide sufficient airflow. Due to the sheer volume and speed of air movement required, the fans may be powered by stationary turbofan
Turbofan
The turbofan is a type of airbreathing jet engine that is widely used for aircraft propulsion. A turbofan combines two types of engines, the turbo portion which is a conventional gas turbine engine, and the fan, a propeller-like ducted fan...

 engines rather than electric motors.

The airflow created by the fans that is entering the tunnel is itself highly turbulent due to the fan blade motion (when the fan is blowing air into the test section – when it is sucking air out of the test section downstream, the fan-blade turbulence is not a factor), and so is not directly useful for accurate measurements. The air moving through the tunnel needs to be relatively turbulence-free and laminar. To correct this problem, closely spaced vertical and horizontal air vanes are used to smooth out the turbulent airflow before reaching the subject of the testing.

Due to the effects of viscosity
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...

, the cross-section of a wind tunnel is typically circular rather than square, because there will be greater flow constriction in the corners of a square tunnel that can make the flow turbulent. A circular tunnel provides a smoother flow.

The inside facing of the tunnel is typically as smooth as possible, to reduce surface drag and turbulence that could impact the accuracy of the testing. Even smooth walls induce some drag into the airflow, and so the object being tested is usually kept near the center of the tunnel, with an empty buffer zone between the object and the tunnel walls. There are correction factors to relate wind tunnel test results to open-air results.

Lighting is usually recessed into the circular walls of the tunnel and shines in through windows. If the light were mounted on the inside surface of the tunnel in a conventional manner, the light bulb would generate turbulence as the air blows around it. Similarly, observation is usually done through transparent portholes into the tunnel. Rather than simply being flat discs, these lighting and observation windows may be curved to match the cross-section of the tunnel and further reduce turbulence around the window.

Various techniques are used to study the actual airflow around the geometry and compare it with theoretical results, which must also take into account the Reynolds number and Mach number
Mach number
Mach number is the speed of an object moving through air, or any other fluid substance, divided by the speed of sound as it is in that substance for its particular physical conditions, including those of temperature and pressure...

 for the regime of operation.

Pressure measurements

Pressure across the surfaces of the model can be measured if the model includes pressure taps. This can be useful for pressure-dominated phenomena, but this only accounts for normal forces on the body.

Force and moment measurements

With the model mounted on a force balance, one can measure lift, drag, lateral forces, yaw, roll, and pitching moments over a range of angle of attack
Angle of attack
Angle of attack is a term used in fluid dynamics to describe the angle between a reference line on a lifting body and the vector representing the relative motion between the lifting body and the fluid through which it is moving...

. This allows one to produce common curves such as lift coefficient
Lift coefficient
The lift coefficient is a dimensionless coefficient that relates the lift generated by a lifting body, the dynamic pressure of the fluid flow around the body, and a reference area associated with the body...

 versus angle of attack (shown).

Note that the force balance itself creates drag and potential turbulence that will affect the model and introduce errors into the measurements. The supporting structures are therefore typically smoothly shaped to minimize turbulence.

Flow visualization

Because air is transparent it is difficult to directly observe the air movement itself. Instead, multiple methods of both quantitative and qualitative flow visualization methods have been developed for testing in a wind tunnel.

Qualitative methods

  • Smoke

  • Tufts

Tufts are applied to a model and remain attached during testing. Tufts can be used to gauge air flow patterns and flow separation.
  • Evaporating suspensions

Evaporating suspensions are simply a mixture of some sort or fine powder, talc, or clay mixed into a liquid with a low latent heat of evaporation. When the wind is turned on the liquid quickly evaporates leaving behind the clay in a pattern characteristic of the air flow.
When oil is applied to the model surface it can clearly show the transition from laminar to turbulent flow as well as flow separation.
Fog (usually from water particles) is created with an ultrasonic
Ultrasonics
Ultrasonics is a term meaning the application of ultrasound. It is often used in industry as a shorthand term for any equipment employing ultrasonic principles....

 piezoelectric nebulizer
Nebulizer
In medicine, a nebulizer is a device used to administer medication in the form of a mist inhaled into the lungs....

. The fog is transported inside the wind tunnel (preferably of the closed circuit & closed test section type). An electrically heated grid is inserted before the test section which evaporates the water particles at its vicinity thus forming fog sheets. The fog sheets function as streamlines over the test model when illuminated by a light sheet.
Video of a wind tunnel fog visualization
  • Sublimation


If the air movement in the tunnel is sufficiently non-turbulent, a particle stream released into the airflow will not break up as the air moves along, but stay together as a sharp thin line. Multiple particle streams released from a grid of many nozzles can provide a dynamic three-dimensional shape of the airflow around a body. As with the force balance, these injection pipes and nozzles need to be shaped in a manner that minimizes the introduction of turbulent airflow into the airstream.

High-speed turbulence and vortices can be difficult to see directly, but strobe lights and film cameras or high-speed digital cameras can help to capture events that are a blur to the naked eye.

High-speed cameras are also required when the subject of the test is itself moving at high speed, such as an airplane propeller. The camera can capture stop-motion images of how the blade cuts through the particulate streams and how vortices are generated along the trailing edges of the moving blade.

Classification

There are many different kinds of wind tunnels, an overview is given in the list below:
  • Low-speed wind tunnel
  • High-speed wind tunnel
  • Supersonic wind tunnel
  • Hypersonic wind tunnel
    Hypersonic wind tunnel
    A hypersonic wind tunnel is designed to generate a hypersonic flow field in the working section. The speed of these tunnels vary from Mach 5 to 15. As with supersonic wind tunnels, these types of tunnels must run intermittently with very high pressure ratios when initializing.Since the temperature...

  • Subsonic and transonic wind tunnel

List of wind tunnels

  • Modine Wind Tunnels, Climatic Wind Tunnel Testing, Large Truck and Automotive
  • AeroDyn Wind Tunnel, Full Scale NASCAR Racecars
  • A2 Wind Tunnel, Full scale general purpose
  • Eight-Foot High Speed Tunnel
    Eight-Foot High Speed Tunnel
    The Eight-Foot High Speed Tunnel, also known as Eight-Foot Transonic Tunnel, is a wind tunnel at NASA's Langley Research Center in Hampton, Virginia. It is a National Historic Landmark....

  • Full Scale 30- by 60-Foot Tunnel
    Full Scale 30- by 60-Foot Tunnel
    The Full-Scale Tunnel was a wind tunnel at NASA's Langley Research Center. It is a National Historic Landmark....

  • Trisonic Wind Tunnel
    Trisonic wind tunnel
    The Trisonic Wind Tunnel was a wind tunnel in El Segundo, California. It was built by North American Aviation in the 1950s. The tunnel was so named because it was capable of testing in three speed regimes – subsonic, transonic, and supersonic, with a maximum speed of Mach 3.5.The TWT was a...

  • Unitary Plan Wind Tunnel
    Unitary Plan Wind Tunnel
    The Unitary Plan Wind Tunnel, located at the NASA Ames Research Center in Moffett Federal Airfield, Mountain View, California, USA, was a research facility used extensively to design and test new generations of aircraft, both commercial and military, as well as NASA space vehicles, including the...

  • Wind Shear's Full Scale, Rolling Road, Automotive Wind Tunnel
    Wind Shear's Full Scale, Rolling Road, Automotive Wind Tunnel
    In January 2008 Wind Shear, a division of US machine tool builder Haas Automation, completed construction on one of the most advanced automotive wind tunnels in the world. The full scale tunnel is located adjacent to Concord Regional Airport in Concord, North Carolina...

  • Variable Density Tunnel
    Variable Density Tunnel
    The Variable Density Tunnel was a wind tunnel at NASA's Langley Research Center. It is a National Historic Landmark. It was the world's first variable density wind tunnel that allowed accurate testing with small-scale models...


Aquadynamic Flume

The aerodynamic principles of the wind tunnel work equally on watercraft, except the water is more viscous and so imposes a greater forces on the object being tested. A looping flume
Flume
A flume is an open artificial water channel, in the form of a gravity chute, that leads water from a diversion dam or weir completely aside a natural flow. Often, the flume is an elevated box structure that follows the natural contours of the land. These have been extensively used in hydraulic...

 is typically used for underwater aquadynamic testing. The interaction between 2 different types of fluids means that pure windtunnel testing is only partly relevant. However, a similar sort of research is done in a towing tank

Low-speed Oversize Liquid Testing

Air is not always the best test medium to study small-scale aerodynamic principles, due to the speed of the air flow and airfoil movement. A study of fruit fly wings designed to understand how the wings produce lift was performed using a large tank of mineral oil and wings 100 times larger than actual size, in order to slow down the wing beats and make the vortices generated by the insect wings easier to see and understand.

Fan testing

Wind tunnel tests are also performed to measuring the air movement of the fans at a specific pressure exactly. By determining the environmental circumstances during the measuring and by revising the air-tightness afterwards, the standardization of the data is warranted.
There are 2 possible ways of measurement: a complete fan or an impeller
Impeller
An impeller is a rotor inside a tube or conduit used to increase the pressure and flow of a fluid.- Impellers in pumps :...

 on a hydraulic installation. Two measuring tubes enable measurements of lower air currents (< 30.000 m³/h) as well as higher air currents (< 60.000 m³/h). The determination of the Q/h curve of the fan is one of the main objectives. To determine this curve (and to define other parameters) air technical, mechanical as well as electro technical data are measured:

Air technical:
  • Static pressure difference (Pa)
  • Amount of moved air (m³/h)
  • Average air speed (m/s)
  • Specific efficiency (W/1000m³/h)
  • Efficiency


Electro technical:
  • Tension (V)
  • Current (A)
  • Cos φ
  • Admitted power (W) fan / impeller
    Impeller
    An impeller is a rotor inside a tube or conduit used to increase the pressure and flow of a fluid.- Impellers in pumps :...

  • Rotations per minute (RPM)


The measurement can take place on the fan or in the application in which the fan is used.

Wind engineering testing

In Wind Engineering
Wind engineering
Wind engineering analyzes effects of wind in the natural and the built environment and studies the possible damage, inconvenience or benefits which may result from wind. In the field of structural engineering it includes strong winds, which may cause discomfort, as well as extreme winds, such as in...

, Wind Tunnel Tests are often used to measure the velocity around, and forces or pressures upon structures. Usually very tall buildings, buildings with unusual or complicated shapes (such as a tall building with a parabolic or a hyperbolic shape), cable suspension bridges or cable stayed bridges are analysed in specialized atmospheric boundary layer wind tunnels. These feature a long upwind section to accurately represent the wind speed and turbulence profile acting on the structure. Wind tunnel tests provide the necessary design pressure measurements for use in the dynamic analysis of the structure.

See also

  • Wind tunnel testing of fans
    Wind tunnel testing of fans
    Wind tunnel tests are performed to measure the air movement of axial fans at a specific pressure exactly. By determining the environmental circumstances during the measuring and by revising the air-tightness afterwards, the standardization of the data is warranted....

  • Automobile design
  • Vertical wind tunnel
    Vertical wind tunnel
    A vertical wind tunnel is a wind tunnel which moves air up in a vertical column. It is a recreational wind tunnel, frequently advertised as "indoor skydiving" or "bodyflight". It is also a popular training tool for skydivers....

  • Sting (fixture)
    Sting (fixture)
    In experimental fluid mechanics, a sting is a test fixture on which models are mounted for testing, e.g., in a wind tunnel. A sting is usually a long shaft attaching to the downstream end of the model so that it does not disturb flow over the model....

  • Arsenal (Vienna)
    Arsenal (Vienna)
    The Arsenal is a former military complex of buildings in the south-east of Vienna in the third district.Several brick buildings in a rectangle layout make up the complex which is located on a bank south of the Landstraßer Gürtel...

    , climatic wind tunnel centre used by the rail industry
  • Doriot Climatic Chambers
    Doriot Climatic Chambers
    The Doriot Climatic Chambers are a pair of very large, highly specialized wind tunnels/environmental chambers located at the U.S. Army’s Soldier Systems Center in Natick, Massachusetts...

    , climatic wind tunnel centre operated by the United States military
  • Whirling arm

External links


The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK