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100-491: By early 2019, following extensive wind tunnel testing at NASA Ames Research Center , an optimized truss and more sweep for the 170 ft (52 m) span wing allowed flying higher and faster, up from Mach 0.70–0.75 to Mach 0.80 like current jetliners . Compared to aircraft with cantilevered wings, fuel burn will be reduced by 8-10%, and the technology should be ready by 2030-2035. Aspect ratios up to 27 were evaluated, up from 8-10 for current narrow-bodies . The design

200-403: A tubular fan, was patented in 1893 by Paul Mortier, and is used extensively in heating, ventilation, and air conditioning (HVAC), especially in ductless split air conditioners. The fan is usually long relative to its diameter, so the flow remains approximately two-dimensional away from the ends. The cross-flow fan uses an impeller with forward-curved blades, placed in a housing consisting of

300-505: 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 (3 to 6 m/s). Otto Lilienthal used a rotating arm to accurately measure wing airfoils with varying angles of attack , establishing their lift-to-drag ratio polar diagrams, but

400-486: A "squirrel cage" (because of its general similarity in appearance to exercise wheels for pet rodents) or "scroll fan", the centrifugal fan has a moving component (called an impeller ) that consists of a central shaft about which a set of blades that form a spiral , or ribs, are positioned. Centrifugal fans blow air at right angles to the intake of the fan and spin the air outwards to the outlet (by deflection and centrifugal force ). The impeller rotates, causing air to enter

500-513: A British engineer, demonstrated the successful use of a fan system to draw out stagnant air from coal mines in 1727—ventilation was essential in coal mines to prevent asphyxiation—and soon afterward he installed a similar apparatus in Parliament. The civil engineer John Smeaton , and later John Buddle installed reciprocating air pumps in the mines in the North of England, though the machinery

600-516: A centrifugal blower in 1897, and determined the drag coefficients of flat plates, cylinders and spheres. Danish inventor Poul la Cour applied wind tunnels in his process of developing and refining the technology of wind turbines in the early 1890s. Carl Rickard Nyberg used a wind tunnel when designing his Flugan from 1897 and onwards. In a classic set of experiments, the Englishman Osborne Reynolds (1842–1912) of

700-612: A comparatively low volume. A fan blade will often rotate when exposed to an air-fluid stream, and devices that take advantage of this, such as anemometers and wind turbines , often have designs similar to that of a fan. Typical applications include climate control and personal thermal comfort (e.g., an electric table or floor fan), vehicle engine cooling systems (e.g., in front of a radiator), machinery cooling systems (e.g., inside computers and audio power amplifiers ), ventilation, fume extraction, winnowing (e.g., separating chaff from cereal grains), removing dust (e.g. sucking as in

800-400: A cross-flow fan is covered to create a pressure differential. A cross-flow fan has two walls outside the impeller and a thick vortex wall inside. The radial gap decreases in the direction of the impeller rotation. The rear wall has a log-spiral profile, while the vortex stabilizer is a thin horizontal wall with a rounded edge. The resultant pressure difference allows air to flow straight through

900-483: 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 , the cross-section of a wind tunnel is typically circular rather than square, because there will be greater flow constriction in

1000-692: A few hours to protect from fan death. Typical room electrical fans consume 50 to 100 watts of power, while air-conditioning units use 500 to 4000 watts; fans use less electricity but do not cool the air, simply providing evaporative cooling of sweat. Commercial fans are louder than AC units and can be disruptively loud. According to the U.S. Consumer Product Safety Commission, reported incidents related to box fans include, fire (266 incidents), potential fire (29 incidents), electrocution (15), electric shock (4 incidents), and electrical hazard (2 incidents). Injuries related to AC units mostly relate to their falling from buildings. Mechanical revolving blade fans are made in

1100-497: 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 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. The aerodynamic properties of an object can not all remain

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1200-463: A larger airmass through a circular or oval-shaped opening via a low-pressure area created by an airfoil surface shape (the Coandă effect ). Air curtains and air doors also utilize this effect to help retain warm or cool air within an otherwise exposed area that lacks a cover or door. Air curtains are commonly used on open-face dairy, freezer, and vegetable displays to help retain chilled air within

1300-405: A pair of fans driven by 4,000 hp (3,000 kW) electric motors. The layout was a double-return, closed-loop format and could accommodate many full-size real aircraft as well as scale models. The tunnel was eventually closed and, even though it was declared a National Historic Landmark in 1995, demolition began in 2010. Until World War II, the world's largest wind tunnel, built in 1932–1934,

1400-413: A rear wall and a vortex wall. Unlike radial machines, the main flow moves transversely across the impeller, passing the blading twice. The flow within a cross-flow fan may be broken up into three distinct regions: a vortex region near the fan discharge, called an eccentric vortex, the through-flow region, and a paddling region directly opposite. Both the vortex and paddling regions are dissipative, and as

1500-496: A relatively large volume of air. Before powered fans were widely accessible, their use related to the social divide between social classes. In Britain and China, they were initially only installed in the buildings of Parliament and in noble homes. In Ancient Egypt (3150 BC), servants were required to fan Pharaohs and important figures. In parts of the world such as India, where the temperature reaches above 100 °F (38 °C), standing and electric box fans are essential in

1600-463: A result, only a portion of the impeller imparts usable work on the flow. The cross-flow fan, or transverse fan, is thus a two-stage partial admission machine. The popularity of the crossflow fan in HVAC comes from its compactness, shape, quiet operation, and ability to provide a high-pressure coefficient. Effectively a rectangular fan in terms of inlet and outlet geometry, the diameter readily scales to fit

1700-630: A room create a wind chill by increasing the heat transfer coefficient but do not lower temperatures directly. Fans used to cool electrical equipment or in engines or other machines cool the equipment directly by exhausting hot air into the cooler environment outside of the machine so that cooler air flows in. Three main types of fans are used for moving air, axial , centrifugal (also called radial ) and cross flow (also called tangential ). The American Society of Mechanical Engineers Performance Testing Code 11 (PTC) provides standard procedures for conducting and reporting tests on fans, including those of

1800-462: A series/parallel hybrid electric propulsor based on Rolls-Royce LibertyWorks ' EVE concept of a geared turbofan . A 1.5 MW (2,000 hp) electric motor/generator mounted between the compressor and the variable pitch fan , fed by batteries to boost the takeoff and climb, allows for a smaller engine and improves efficiency by 4.5% over a 3,500 nmi (4,000 mi; 6,500 km) mission. A tail-mounted BLI fan would ingest and reenergize

1900-593: A servant called the punkawallah . For purposes of air conditioning , the Han dynasty craftsman and engineer Ding Huan (fl. 180 CE) invented a manually operated rotary fan with seven wheels that measured 3 m (10 ft) in diameter; in the 8th century, during the Tang dynasty (618–907), the Chinese applied hydraulic power to rotate the fan wheels for air conditioning, while the rotary fan became even more common during

2000-516: A stream of air that entrains ambient air to circulate the ambient air. The system takes up less space than conventional ventilation ducting and can significantly increase the rates of inflow of fresh air and expulsion of stale air. Fans generate noise from the rapid flow of air around blades and obstacles causing vortexes, and from the motor. Fan noise is roughly proportional to the fifth power of fan speed; halving speed reduces noise by about 15 dB . The perceived loudness of fan noise also depends on

2100-646: A trailing edge with forward sweep that generates lift. It was tested in early 2019 at the NASA Ames 11 ft (3.4 m) transonic tunnel, then later in 2019 at the 14 by 22 ft (4.3 by 6.7 m) subsonic tunnel at NASA Langley . A full-scale X-plane is being developed and tested under NASA's Ultra-Efficient Subsonic Transport (UEST) plan, outlined in the New Aviation Horizons flight demonstration from 2023. Boeing proposed to modify an MD-80 powered by turbofan engines, but it could test

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2200-417: A tube, and air is blown around it to study the interaction between the object and the moving air. They are used to test the aerodynamic effects of aircraft , rockets , cars , and buildings . Different wind tunnels range in size from less than a foot across, to over 100 feet (30 m), and can have air that moves at speeds from a light breeze to hypersonic velocities. Usually, large fans move air through

2300-452: A vacuum cleaner), drying (usually in combination with a heat source) and providing draft for a fire. Some fans may be indirectly used for cooling in the case of industrial heat exchangers. While fans are effective at cooling people, they do not cool air. Instead, they work by evaporative cooling of sweat and increased heat convection into the surrounding air due to the airflow from the fans. Thus, fans may become less effective at cooling

2400-452: A wide range of designs. They are used on the floor, table, desk, or hung from the ceiling ( ceiling fan ) and can be built into a window, wall, roof, etc. Tower fans tend to have smaller blades inside. Electronic systems generating significant heat, such as computers , incorporate fans. Appliances such as hair dryers and space heaters also use fans. They move air in air-conditioning systems and in automotive engines. Fans used for comfort inside

2500-431: A wind tunnel type of test during an actual flight in order to refine the computational model. 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, and terrain. The most effective way to simulative external turbulent flow

2600-405: Is blown or sucked through a duct equipped with a viewing port and instrumentation where models 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

2700-578: Is contained within some form of housing, or case. This may direct the airflow, or increase safety by preventing objects from contacting the fan blades. Most fans are powered by electric motors , but other sources of power may be used, including hydraulic motors , handcranks , and internal combustion engines . Mechanically, a fan can be any revolving vane , or vanes used for producing currents of air . Fans produce air flows with high volume and low pressure (although higher than ambient pressure ), as opposed to compressors which produce high pressures at

2800-527: 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 design. For instance, the use of boundary layer wind tunnel modeling can be used as a credit for Leadership in Energy and Environmental Design (LEED) certification through

2900-409: Is often connected to machines with a rotating part rather than being powered separately. This is commonly seen in motor vehicles with internal combustion engines , large cooling systems, locomotives, and winnowing machines, where the fan is connected to the drive shaft or through a belt and pulleys. Another common configuration is a dual-shaft motor, where one end of the shaft drives a mechanism, while

3000-416: Is particularly important in open cockpit race cars such as Indycar and Formula One. Excessive lift forces on the helmet can cause considerable neck strain on the driver, and flow separation on the back side of the helmet can cause turbulent buffeting and thus blurred vision for the driver at high speeds. The advances in computational fluid dynamics (CFD) modelling on high-speed digital computers has reduced

3100-497: Is targeted at 30% better than current Boeing 737 MAX and Airbus A320neo . Using a shortened MD-90 airframe and CFM International RISE engines, the demonstrator is scheduled to fly in 2028, providing the basis for a possible family of 130-to-210-seat aircraft. The full-scale Sustainable Flight Demonstrator (SFD) is designated "X-66A". In August 2023, the MD-90 airframe was ferried to Palmdale Regional Airport for complete rebuild into

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3200-409: 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

3300-686: The Song dynasty (960–1279). During the Heian period (794-1185) in Japan, fans adapted the role of symbolizing social class as well as a mechanical role. The tessen , a Japanese fan used in Feudal times, was a dangerous weapon hidden in plain sight in the shape of a regular fan, a weapon used by samurais when katanas were not ideal. In the 17th century, the experiments of scientists, including Otto von Guericke , Robert Hooke , and Robert Boyle established

3400-531: The University of Manchester 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

3500-556: The World Health Organization (WHO) suggests avoiding fan use above 40 °C (104 °F). Recent studies have shed further light on this issue, though their findings are somewhat contradictory. One study found limited additional benefit from fan use above 35 °C (95 °F), while another study reported a 31% reduction in cardiac stress among elderly individuals using fans at 38 °C (100 °F). Standalone fans are usually powered by an electric motor , often attached directly to

3600-417: The static pressure , and (for compressible flow only) the temperature rise in the airflow. The direction of airflow around a model can be determined by tufts of yarn attached to the aerodynamic surfaces. The direction of airflow approaching a surface can be visualized by mounting threads in the airflow ahead of and aft of the test model. Smoke or bubbles of liquid can be introduced into the airflow upstream of

3700-562: The 1930s, the first art deco fan (the "Silver Swan") was designed by Emerson. By the 1940s, Crompton Greaves of India became the world's largest manufacturer of electric ceiling fans mainly for sale in India, Asia, and the Middle East. By the 1950s, table and stand fans were manufactured in bright colors and were eye-catching. Window and central air conditioning in the 1960s caused many companies to discontinue production of fans, but in

3800-413: The 1960s, wind tunnel testing began to receive widespread adoption for automobiles , not so much to determine aerodynamic forces in the same way as an airplane, but to increase the fuel efficiency of vehicles by reducing the aerodynamic drag. 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

3900-523: 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

4000-466: The United States as part of the plan to exploit German technology developments. For limited applications, computational fluid dynamics (CFD) can supplement 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

4100-403: The United States, many wind tunnels have been decommissioned from 1990 to 2010, 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

Boeing X-66 - Misplaced Pages Continue

4200-460: The X-66. In June 2024, Boeing and Pratt & Whitney announced that a dedicated derivative of the geared turbofan (GTF) engine PW1500G/1900G series, named PW102XG , will be installed. This selection was made, due to weight concerns regarding the previously anticipated application of a PW1100G derivative. Wind tunnel Wind tunnels are machines in which objects are held stationary inside

4300-589: The above, however, that they were simply using the accepted technology of the day, though this was not yet a common technology in America. In France , Gustave Eiffel (1832–1923) built his first open-return wind tunnel in 1909, powered by a 67 hp (50 kW) electric motor, at Champs-de-Mars, near the foot of the tower that bears his name. Between 1909 and 1912 Eiffel ran about 4,000 tests in his wind tunnel, and his systematic experimentation set new standards for aeronautical research. In 1912 Eiffel's laboratory

4400-484: The air standing still and an aircraft moving, an object would be held still and the air moved around it. In this way, a stationary observer could study the flying object in action, and could measure the aerodynamic forces acting on it. The development of wind tunnels accompanied the development of the airplane. Large wind tunnels were built during World War II, and as supersonic aircraft were developed, supersonic wind tunnels were constructed to test them. Wind tunnel testing

4500-400: The airstream to show the path that air takes around the object. Or, small threads can be attached to specific parts to show the airflow at those points. The earliest wind tunnels were invented towards the end of the 19th century, in the early days of aeronautical research, as part of the effort to develop heavier-than-air flying machines. The wind tunnel reversed the usual situation. Instead of

4600-638: The answers out of a wind tunnel." 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 (14 m) and narrows to 20 feet (6.1 m) in diameter. Two 40-foot (12 m) fans were driven by a 40,000 hp electric motor. Large scale aircraft models could be tested at air speeds of 400 mph (640 km/h). During WWII, Germany developed different designs of large wind tunnels to further their knowledge of aeronautics. For example,

4700-446: The application. They are often used in free installations without any housing. There are also some specialised installations. In vehicles, a ducted fan is a method of propulsion in which a fan, propeller or rotor is surrounded by an aerodynamic duct or shroud which enhances its performance to create aerodynamic thrust or lift to transport the vehicle. In ventilation systems, a jet fan, also known as an impulse or induction fan, ejects

4800-441: The available space, and the length is adjustable to meet flow rate requirements for the particular application. Common household tower fans are also cross-flow fans. Much of the early work focused on developing the cross-flow fan for both high- and low-flow-rate conditions and resulted in numerous patents. Key contributions were made by Coester, Ilberg and Sadeh, Porter and Markland, and Eck. One interesting phenomenon particular to

4900-537: The basic principles of vacuum and airflow. The English architect Sir Christopher Wren applied an early ventilation system in the Houses of Parliament that used bellows to circulate air. Wren's design was the catalyst for much later improvement and innovation. The first rotary fan used in Europe was for mine ventilation during the 16th century, as illustrated by Georg Agricola (1494–1555). John Theophilus Desaguliers ,

5000-419: The body if the surrounding air is near body temperature and contains high humidity. Fans made with leaves were prevalent in ancient Egypt and India. In ancient India, they were handheld fans made from bamboo strips or other plant fiber, that could be rotated or fanned to move air. During British rule , the word came to be used by Anglo-Indians to mean a large swinging flat fan, fixed to the ceiling and pulled by

5100-641: The building will collapse. Determining such forces was required before building codes could specify the required strength of such buildings and these tests continue to be used for large or unusual buildings. Wind tunnel testing was first applied to automobiles as early as the 1920s, on cars such as the Rumpler Tropfenwagen , and later the Chrysler Airflow . Initially, automakers would test out scale models of their cars, but later, full scale automotive wind tunnels were built. Starting in

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5200-427: The business world for customer comfort and an efficient work environment. Fans have become solar-powered, energy-efficient, and battery-powered in places with unreliable energy sources. In South Korea, fans play a part in an old wives tale . Many older South Korean citizens believe in the unscientific and unsupported myth of fan death due to excessive use of an electric fan; Korean electric fans usually turn off after

5300-460: The cabinet using a laminar airflow circulated across the display opening. The airflow is typically generated by a mechanical fan of any type, as described in this article, and is hidden in the base of the display cabinet. HVAC linear slot diffusers also utilize this effect to increase airflow evenly in rooms compared to registers while reducing the energy used by the air handling unit blower . Fans may be installed in various ways, depending on

5400-555: The case for the foreseeable future. Studies have been done and others are underway 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, or research drones, have replaced some of the traditional uses of wind tunnels. The world's fastest wind tunnel as of 2019 is the LENS-X wind tunnel, located in Buffalo, New York. Air

5500-483: 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 ' use of a simple wind tunnel in 1901 to study the effects of airflow over various shapes while developing their Wright Flyer was in some ways revolutionary. It can be seen from

5600-637: The centrifugal, axial, and mixed flows. Axial-flow fans have blades that force air to move parallel to the shaft about which the blades rotate. This type of fan is used in a wide variety of applications, ranging from small cooling fans for electronics to the giant fans used in cooling towers . Axial flow fans are applied in air conditioning and industrial process applications. Standard axial flow fans have diameters of 300–400 mm or 1,800–2,000 mm and work under pressures up to 800 Pa . Special types of fans are used as low-pressure compressor stages in aircraft engines. Examples of axial fans are: Often called

5700-402: The consumer market in 2009 have popularized a 1981 design by Toshiba that produces a fan that has no exposed fan blades or other visibly moving parts (unless augmented by other features such as for oscillation and directional adjustment). A relatively small quantity of air from a high-pressure-bladed impeller fan, which is contained inside the base rather than exposed, induces the slower flow of

5800-428: 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

5900-418: The cross-flow fan is that, as the blades rotate, the local air incidence angle changes. The result is that in certain positions, the blades act as compressors (pressure increase), while at other azimuthal locations, the blades act as turbines (pressure decrease). Since the flow enters and exits the impeller radially, the crossflow fan has been studied and prototyped for potential aircraft applications. Due to

6000-403: The demand for wind tunnel testing, but has not completely eliminated it. Many real-world problems can still not be modeled accurately enough by CFD to eliminate the need for physical tests in wind tunnels. Air velocity and pressures are measured in several ways in wind tunnels. Air velocity through the test section is determined by Bernoulli's principle . Measurement of the dynamic pressure ,

6100-414: The direction of smoke from a ship's stack, to whether a given airplane would fly. Progress at Aachen, I felt, would be virtually impossible without a good wind tunnel. When von Kármán began to consult with Caltech he worked with Clark Millikan and Arthur L. Klein. He objected to their design and insisted on a return flow making the device "independent of the fluctuations of the outside atmosphere". It

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6200-416: The end of the war, Germany had at least three different supersonic wind tunnels, with one capable of Mach 4.4 (heated) airflows. A large wind tunnel under construction near Oetztal , Austria would have had two fans directly driven by two 50,000 horsepower hydraulic turbines . The installation was not completed by the end of the war and the dismantled equipment was shipped to Modane , France in 1946 where it

6300-578: The fan near the shaft and move perpendicularly from the shaft to the opening in the scroll-shaped fan casing. A centrifugal fan produces more pressure for a given air volume, and is used where this is desirable such as in leaf blowers , blowdryers , air mattress inflators, inflatable structures , climate control in air handling units and various industrial purposes. They are typically noisier than comparable axial fans (although some types of centrifugal fans are quieter such as in air handling units). The cross-flow or tangential fan, sometimes known as

6400-466: The fan, even though the fan blades counter the flow of air on one side of the rotation. Cross-flow fans give airflow along the entire width of the fan; however, they are noisier than ordinary centrifugal fans. Cross-flow fans are often used in ductless air conditioners , air doors , in some types of laptop coolers , in automobile ventilation systems, and for cooling in medium-sized equipment such as photocopiers . Dyson Air Multiplier fans introduced to

6500-465: The fans would force the incoming air upward and through vents in the ceiling. Improvements in the technology were made by James Nasmyth , Frenchman Theophile Guibal and J. R. Waddle. Between 1882 and 1886 Schuyler Wheeler invented a fan powered by electricity. It was commercially marketed by the American firm Crocker & Curtis electric motor company. In 1885 a desktop direct drive electric fan

6600-479: 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 John 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 . Konstantin Tsiolkovsky built an open-section wind tunnel with

6700-411: The frequency distribution of the noise. This depends on the shape and distribution of moving parts, especially of the blades, and of stationary parts, struts in particular. Like with tire treads , and similar to the principle of acoustic diffusors , an irregular shape and distribution can flatten the noise spectrum, making the noise sound less disturbing. The inlet shape of the fan can also influence

6800-422: The mid-1970s, with an increasing awareness of the cost of electricity and the amount of energy used to heat and cool homes, turn-of-the-century styled ceiling fans became popular again as both decorative and energy-efficient. In 1998 William Fairbank and Walter K. Boyd invented the high-volume low-speed (HVLS) ceiling fan , designed to reduce energy consumption by using long fan blades rotating at low speed to move

6900-493: The motor's output, with no gears or belts. The motor is either hidden in the fan's center hub or extends behind it. For big industrial fans , three-phase asynchronous motors are commonly used, may be placed near the fan, and drive it through a belt and pulleys . Smaller fans are often powered by shaded pole AC motors , or brushed or brushless DC motors . AC-powered fans usually use mains voltage, while DC-powered fans typically use low voltage, typically 24V, 12V, or 5 V. The fan

7000-578: The noise levels generated by the fan. The optimal temperature for using a fan to cool down remains uncertain. While fans are commonly used to lower body temperature through evaporative cooling, there is a point at which the convection effect of moving air can counteract this benefit. This temperature, at which fan use may become detrimental, is currently unknown. Health organizations offer varying guidance on fan usage in high temperatures. The Centers for Disease Control and Prevention (CDC) advises against fan use when temperatures exceed 32.2 °C (90 °F), while

7100-407: The object and the tunnel walls. There are correction factors to relate wind tunnel test results to open-air results. Fan (machine) A fan is a powered machine that creates airflow. A fan consists of rotating vanes or blades, generally made of wood, plastic, or metal, which act on the air. The rotating assembly of blades and hub is known as an impeller , rotor , or runner . Usually, it

7200-436: The other has a fan mounted on it to cool the motor itself. Window air conditioners commonly use a dual-shaft fan to operate separate fans for the interior and exterior parts of the device. Where electrical power or rotating parts are not readily available, other methods may drive fans. High-pressure gases such as steam can drive a small turbine , and high-pressure liquids can drive a pelton wheel , either of which can provide

7300-431: The pressure at each hole. Pressure distributions can more conveniently be measured by the use of pressure-sensitive paint , 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

7400-406: The rotational direction of the fan, causing a large Magnus force , similar to a spinning leading-edge cylinder. Another configuration utilizing a crossflow fan for thrust and flow control is the propulsive wing , another experimental concept prototype initially developed in the 1990s and 2000s. In this design, the crossflow fan is placed near the trailing edge of a thick wing and draws the air from

7500-417: The rotational drive for a fan. Large, slow-moving energy sources, such as a flowing river, can also power a fan using a water wheel and a series of step-down gears or pulleys to increase the rotational speed to that required for efficient fan operation. Electric fans used for ventilation may be powered by solar panels instead of mains current. This is an attractive option because once the capital costs of

7600-592: The same for a scaled model. However, by observing certain similarity rules, a very satisfactory correspondence between the aerodynamic properties of a scaled model and a full-size object can be achieved. The choice of similarity parameters depends on the purpose of the test, but the most important conditions to satisfy are usually: In certain particular test cases, other similarity parameters must be satisfied, such as e.g. Froude number . English military engineer and mathematician Benjamin Robins (1707–1751) invented

7700-403: The sheer volume and speed of air movement required, the fans may be powered by stationary turbofan 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

7800-500: The slow airflow over the fuselage. A full-scale demonstrator based on the McDonnell Douglas/Boeing MD-90 was announced on January 18, 2023, with NASA funding $ 425 million over seven years while Boeing and its partners will invest the remainder of the agreed $ 725 million, as the airframer had already spent $ 110 million in sustainable aviation research. Combined with better propulsion and materials, efficiency

7900-507: The solar panel have been covered, the resulting electricity is free. If ventilation needs are greatest during sunny weather, a solar-powered fan can be suitable. A typical example uses a detached 10- watt , 12 in × 12 in (30 cm × 30 cm) solar panel and is supplied with appropriate brackets, cables , and connectors . It can be used to ventilate up to 1,250 square feet (116 m ) of area and can move air at up to 800 cubic feet per minute (400 L/s). Because of

8000-426: The test model, and their path around the model can be photographed (see particle image velocimetry ). Aerodynamic forces on the test model are usually measured with beam balances , connected to the test model with beams, strings, or cables. The 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

8100-556: The test results. In the real world, the vehicle is moving while the road and air are stationary. In a wind tunnel test, the road must also be moved past a vehicle along with air being blown around it. This has been accomplished with moving belts under the test vehicle to simulate the moving road, and very similar devices are used in wind tunnel testing of aircraft take-off and landing configurations. Sporting equipment has also studied in wind tunnels, including golf clubs, golf balls, bobsleds, cyclists, and race car helmets. Helmet aerodynamics

8200-455: The two-dimensional nature of the flow, the fan can be integrated into a wing for use in both thrust production and boundary-layer control. A configuration that utilizes a crossflow fan located at the wing leading edge is the FanWing design concept initially developed around 1997 and under development by a company of the same name. This design creates lift by deflecting the wake downward due to

8300-459: The wind stream is upwards for the testing of models in spin situations and the concepts and engineering designs for the first primitive helicopters flown in the US. 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 designed to provide supersonic flow. The observation or instrumentation chamber ("test section")

8400-404: The wind tunnel at Peenemünde was a novel wind tunnel design that allowed for high-speed airflow research, but brought several design challenges regarding constructing a high-speed wind tunnel at scale. However, it successfully 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. By

8500-516: The wind tunnel, while the object being tested is held stationary. The object can be an aerodynamic test object such as a cylinder or an airfoil, an individual component of an aircraft, a small model of the vehicle, or, in the largest tunnels, even a full-sized vehicle. Different measurements can be taken from these tests. The aerodynamic forces on the entire object can be measured, or on individual components of it. The air pressure at different points can be measured with sensors. Smoke can be introduced into

8600-406: The wing's suction (top) surface. By doing this, the propulsive wing is nearly stall-free, even at extremely high angles of attack, producing very high lift. However, the fanwing and propulsive wing concepts remain experimental and have only been used for unmanned prototypes. A cross-flow fan is a centrifugal fan in which the air flows straight through the fan instead of at a right angle. The rotor of

8700-583: 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 (370 kW) electric motor drove the paddle type fan blades. In 1931 the NACA built a 30 by 60 feet (9.1 by 18.3 m) full-scale wind tunnel at Langley Research Center in Hampton, Virginia. The tunnel was powered by

8800-550: Was Theodore von Kármán 's teacher at Göttingen University and suggested the construction of a wind tunnel for tests of airships they were designing. The vortex street of turbulence downstream of a cylinder was tested in the tunnel. When he later moved to Aachen University he recalled use of this facility: I remembered the wind tunnel in Göttingen was started as a tool for studies of Zeppelin behavior, but that it had proven to be valuable for everything else from determining

8900-460: Was an arrangement followed by a number of wind tunnels later built; in fact the open-return low-speed wind tunnel is often called the Eiffel-type wind tunnel. 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

9000-608: Was commercially available by Stout, Meadowcraft & Co. in New York. In 1882, Philip Diehl developed the world's first electric ceiling mounted fan . During this intense period of innovation, fans powered by alcohol, oil, or kerosene were common around the turn of the 20th century. In 1909, KDK of Japan pioneered the invention of mass-produced electric fans for home use. In the 1920s, industrial advances allowed steel fans to be mass-produced in different shapes, bringing fan prices down and allowing more homeowners to afford them. In

9100-522: Was completed in 1930 and used for Northrop Alpha testing. In 1939 General Arnold asked what was required to advance the USAF, and von Kármán answered, "The first step is to build the right wind tunnel." On the other hand, after the successes of the Bell X-2 and prospect of more advanced research, he wrote, "I was in favor of constructing such a plane because I have never believed that you can get all

9200-493: Was considered of strategic importance during the Cold War for development of aircraft and missiles. Other problems are also studied with wind tunnels. The effects of wind on man-made structures need to be studied when buildings became tall enough to be significantly affected by the wind. Very tall buildings present large surfaces to the wind, and the resulting forces have to be resisted by the building's internal structure or else

9300-551: Was lacking the notions of induced drag and Reynolds numbers . 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 (1824–1908), a Council Member of the Aeronautical Society of Great Britain , addressed these issues by inventing, designing and operating

9400-595: Was liable to breaking down. In 1849 a 6m radius steam-driven fan, designed by William Brunton , was made operational in the Gelly Gaer Colliery of South Wales . The model was exhibited at the Great Exhibition of 1851. Also in 1851 David Boswell Reid , a Scottish doctor installed four steam-powered fans in the ceiling of St George's Hospital in Liverpool so that the pressure produced by

9500-456: Was 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. The Chalais-Meudon wind tunnel was used by ONERA under the name S1Ch until 1976 in the development of, e.g., the Caravelle and Concorde airplanes. Today, this wind tunnel is preserved as a national monument. Ludwig Prandtl

9600-412: Was moved to Auteuil, a suburb of Paris, where his wind tunnel with a two-metre test section is still operational today. Eiffel significantly improved the efficiency of the open-return wind tunnel by enclosing the test section in a chamber, designing a flared inlet with a honeycomb flow straightener and adding a diffuser between the test section and the fan located at the downstream end of the diffuser; this

9700-425: Was poured on 22 June 1942 on a site that eventually would become Calspan , where the wind tunnel still operates. By the end of World War II, 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 250 mph (400 km/h) and a vertical wind tunnel at Wright Field, Ohio, where

9800-463: Was presented at the January 2019 American Institute of Aeronautics and Astronautics (AIAA) conference and the wing folds outboard of the truss to enable its use of airport gates like the 118 ft (36 m)-span 737. ( ICAO aerodrome code C) Later the wing was improved with 20° of sweep and moved forward, the truss section was optimised, tapered with an increased root chord, and optimized with

9900-469: Was re-erected and is still operated there by the ONERA . With its 26 ft (8 m) test section and airspeed up to Mach 1, it is the largest transonic wind tunnel facility in the world. Frank Wattendorf reported on this wind tunnel for a US response. On 22 June 1942, Curtiss-Wright financed construction of one of the nation's largest subsonic wind tunnels in Buffalo, NY. The first concrete for building

10000-560: Was then placed at the proper location in the throat or nozzle for the desired airspeed. In the United States, concern over the lagging of American research facilities compared to those built by the Germans led to the Unitary Wind Tunnel Plan Act of 1949, which authorized expenditure to construct new wind tunnels at universities and at military sites. Some German war-time wind tunnels were dismantled for shipment to

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