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60-606: On the eve of Thursday, October 31, at 6:13 pm, the Maria fire was reported burning at the top of South Mountain between Santa Paula and Somis and was seen making an aggressive run southwest towards the community of Somis as the fire expanded throughout that evening. Heavily influenced by 20-30 mph winds within the canyons, the fire became a full scale conflagration within its first several hours of burning, growing from 50 to 750 acres inside an hour, to over 4,000 acres (16 km) by 9:45 pm. The fire worked its way north towards Santa Paula in

120-505: 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

180-516: 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

240-483: 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

300-497: 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

360-464: A metal pipe on the ground after an electrical conductor separated. This wildfire -related article is a stub . You can help Misplaced Pages by expanding it . Santa Clara River Valley The Santa Clara River Valley is a rural, mainly agricultural valley in Ventura County, California that has been given the moniker Heritage Valley by the namesake tourism bureau. The valley includes

420-405: 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,

480-417: 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

540-431: 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

600-405: 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

660-603: Is bordered by the Topatopa Mountains , Los Padres National Forest , and Sespe Condor Sanctuary to the north and the Santa Susana Mountains to the south. The valley stretches from the boundary of northwest Los Angeles County and the northern Santa Clarita Valley on the east to the Oxnard Plain on the west marked by South Mountain on the south bank of the river. The Santa Clarita Valley

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720-527: 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

780-562: Is part of the upper watershed of the river. The valley has been called one of the "most dangerous wind and fire corridors in Southern California." It forms a connection between the high desert and the coast, which serves as a "wind-tunnel -like-corridor" for funneling Santa Ana winds , which spread wildfires. This served to spread the Maria Fire , one of the 2019 California wildfires . This valley has also suffered through

840-416: 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

900-409: 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

960-714: The Saddleridge Fire in 2019, the Creek Fire and the Thomas Fire in 2017, and the Sayre Fire in 2008. Further information: Great Flood of 1862 The failure and near complete collapse of the St. Francis Dam took place in the middle of the night on March 12, 1928. The dam was holding a full reservoir of 12.4 billion gallons (47 billion liters) of water that surged down San Francisquito Canyon and emptied into

1020-508: The Santa Clara River Valley , whose topography can serve as a wind tunnel for Santa Ana winds . Mandatory evacuations were ordered for a wide swath of over 1,800 homes surrounding the fire area, affecting over 7,500 residents. Shortly before 11 pm, a drone had been reported flying over the fireline which immediately caused the suspension and grounding of all nighttime water-dropping helicopters that were currently fighting

1080-531: 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

1140-455: The post-war urban development that has almost entirely eliminated citrus cultivation throughout most of Southern California. 34°22′0″N 118°59′0″W  /  34.36667°N 118.98333°W  / 34.36667; -118.98333 This Ventura County, California –related article is a stub . You can help Misplaced Pages by expanding it . Wind tunnel Wind tunnels are machines in which objects are held stationary inside

1200-417: 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

1260-413: 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

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1320-475: The Maria Fire, along with helicopters including an Erickson Skycrane . Initial inquiries into the cause or origin of the Maria fire revealed that Southern California Edison (SCE), the power utility operating in the area, had re-energized 16,000 volt transmission lines in the vicinity roughly 13 minutes before first reports of the fire were received. The lines were de-energized beforehand specifically to avoid

1380-602: The Santa Clara River, flowing down the river valley to the ocean. A footpath through the valley was the only route linking the San Fernando and San Buenaventura missions for 18th-century Spanish missionaries. Thomas Bard launched a campaign in the 1870s to build a road through the valley as he wanted to connect the new Hueneme wharf with ore mines in Inyo County The valley is an exception to

1440-523: 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

1500-466: 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

1560-403: 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

1620-589: 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

1680-484: 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

1740-400: 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

1800-638: 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,

1860-641: 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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1920-555: 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

1980-483: 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

2040-581: The communities of Santa Paula , Fillmore , Piru and the national historic landmark of Rancho Camulos . Named for the Santa Clara River , which winds through the valley before emptying into the Pacific Ocean between the cities of Ventura and Oxnard , the tourist bureau describes it as "Southern California's last pristine agricultural valley nestled along the banks of the free-flowing Santa Clara River." The Santa Clara River Valley

2100-428: 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

2160-403: 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 ,

2220-414: 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

2280-416: 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

2340-505: The fire. This hazard then allowed the incident to continue its critical rate of spread virtually unchecked. By 11:45 pm, the fire had reportedly grown to 7,400 acres with zero containment as the fire progressed predominantly westward. During the day of November 1, three different DC-10 air tankers contracted to the US Forest Service (910, 911 and 914) and flying from Santa Maria and San Bernardino airports made multiple runs on

2400-479: 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

2460-512: The possibility of its power lines causing fires due to the high winds in the area. SCE issued a statement indicating that it had no specific information on the cause of the fire and that it would "cooperate with the appropriate investigative agencies if asked to do so." The final report issued in October 2020 on the cause of the fire cited a combination of extreme wind conditions and a power line owned by California Resources Corporation that touched

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2520-431: 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

2580-592: 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

2640-403: 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

2700-426: 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

2760-556: 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

2820-459: 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")

2880-404: 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

2940-516: 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

3000-583: 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

3060-550: 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

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3120-460: 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

3180-522: 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

3240-493: 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

3300-551: 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

3360-456: 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

3420-412: 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

3480-425: 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

3540-469: 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

3600-560: 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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