How fast are wind tunnels

Attention was paid to the exhaust stacks, machine gun installation, and gun sights that projected into the airflow outside the airplane. When the airplane was perfectly smooth and aerodynamically clean, the drag of this faired and sealed airplane was then measured in the FST. This was the baseline drag measurement. Next, one of the protuberances was added back to the smooth configuration, and the drag was measured again, thus identifying the increase in drag due just to this addition.

The tests continued by adding one-by-one each of the drag-causing items, measuring the airplane drag after each addition, until the airplane configuration was fully restored to its original condition. In this fashion, a detailed test base was acquired, identifying which items increased drag, and by how much.

The design of airplanes was not the primary role of the NACA, so these test results were then reported to the manufacturer, giving Brewster the necessary information to modify the design of the airplane in order to reduce its drag. Amazingly, the top speed of the modified Buffalo was increased from to miles per hour, a meaningful 10 percent increase. What a wake-up call to the airplane industry!

The Army and Navy suddenly stood in line for such drag testing in the Full Scale Tunnel on other new aircraft designs. The pioneering test procedure developed by the NACA engineers was labeled drag cleanup. Over the next two-and-a-half years, 18 new prototype military airplanes were thoroughly run through this drag cleanup test procedure, each design benefiting to a greater or lesser extent by the tests. One of the more telling stories that came out of the drag cleanup program was its effect on the P, a beautifully sleek but somewhat unconventional airplane.

Designed by Bell Aircraft, the Army had expectations for the P to be its first fighter to exceed miles per hour in level flight. Production airplanes, however, were expected to weigh about pounds more than the pounds prototype, a weight increase that was predicted to bring its top speed to barely miles per hour.

This did not make General Henry H. Army Air Corps, happy, and certainly did not satisfy the Bell aircraft designers. In addition to these drag cleanup tests, the P also went through a series of flight tests at Langley. These scale models might be entire airplanes in miniature, built at great expense with exacting precision. Or they might just be a single part of an airplane wing or other product.

Engineers mount models into the test section using different methods, but usually, the models are kept stationary using wires or metal poles, which are placed behind the model to avoid causing disruptions in the airflow They may attach sensors to the model that record wind velocity, temperature, air pressure and other variables.

Keep reading to learn more about how wind tunnels help scientists piece together more complicated aerodynamics puzzles and how their findings spur technological advances. Lift and drag are just two elements of aerodynamics forces that come into play inside a wind tunnel. For aircraft testing in particular, there are dozens of variables like pitch, yaw, roll and many others , that can affect the outcome of experiments.

Other factors also come into play during testing no matter what the test subject might be. For example, the quality of the air in the tunnel is changeable and has a tremendous bearing on test results. In addition to carefully gauging the shape and speed of the object or the wind blowing past the object testers must consider the viscosity or tackiness and compressibility bounciness of the air during their experiments.

You don't normally think of air as a sticky substance, of course, but as air moves over an object, its molecules strike its surface and cling to it, if only for an instant. This creates a boundary layer , a layer of air next to the object that affects airflow, just as the object itself does. Altitude, temperature, and other variables can affect viscosity and compressibility, which in turn changes the boundary layer properties and drag, and the aerodynamics of the test object as a whole.

Figuring out just how all these conditions affect the test object requires a system of sensors and computers for logging sensor data. Pitot tubes are used to measure airflow velocity, but advanced tunnels deploy laser anemometers that detect wind speed by "seeing" airborne particles in the airstream. Pressure probes monitor air pressure and water vapor pressure sensors track humidity. In addition to sensors, visual observations are also extremely useful, but to make airflow visible, scientists rely on various flow visualization techniques.

They may fill the test section with colored smoke or a fine mist of liquid, such as water , to see how air moves over the model. They may apply thick, colored oils to the model to see how the wind pushes the oil along the model's surface. High-speed video cameras may record the smoke or oils as they move to help scientists detect clues that aren't obvious to the unaided eye.

In some cases, lasers are used to illuminate mist or smoke and reveal airflow details. Wind tunnels offer endless configurations for testing limitless ideas and concepts. Keep reading, and you'll see the wildly imaginative tunnels that engineers build when they find the money to turn a breeze of an idea into a full-scale technological tempest. Supersonic and hypersonic tunnels don't use fans.

To generate these breakneck air velocities, scientists use blasts of compressed air stored in pressurized tanks placed upstream of the test section, which is why they are sometimes called blowdown tunnels. Similarly, hypersonic tunnels are sometimes called shock tubes, a reference to the high-powered but very brief blasts they produce.

Both have enormous power requirements, which generally make them best for short or intermittent tests. Air pressure capabilities also differentiate wind tunnels. Some tunnels have controls for lowering or raising air pressure. For example, in testing space vehicles, NASA could set up a tunnel to mimic the low-pressure atmosphere of Mars.

You can also categorize tunnels by size. Some are relatively small, and thus, are useful only for testing scaled-down models or sections of an object. Others are full-scale and big enough to test full-sized vehicles. It's about feet The tunnel uses six, four-story high fans, each driven by six 22, horsepower motors that can drive winds up to mph kph.

Size isn't the only factor in extraordinary wind tunnels. Keep reading, and you'll find out just how modern some of these tunnels really are. Wind tunnels aren't just for pros. You can find plans online for constructing your own wind tunnel at home, or even buy kits with all of the necessary parts included.

There are many types of wind tunnels for all sorts of different purposes. These tunnels are categorized by their characteristics, such as the wind speed they generate in the test section. Subsonic wind tunnels test objects with airflows of less than mph kph. Transonic tunnels cover tunnels cover a wind speed range of mph to mph 1, kph.

Supersonic tunnels generate winds faster than the speed of sound mph or 1, Hypersonic tunnels create scary-fast wind blasts of 3,mph to 11,mph 6, Engineers often need to test multiple aerodynamic and environmental variables simultaneously. That's why some tunnels offer a broad array of testing possibilities in a single location. The Vienna Large Climatic Wind Tunnel, used mostly for automobile and rail vehicle testing, is one such tunnel.

The test section alone is feet meters long, through which wind speeds of up to mph kph flow. Engineers can adjust relative humidity from 10 to 98 percent and push temperatures from as low as degrees to degrees Fahrenheit to 60 Celsius.

True to its name, the Vienna Climatic Tunnel comes complete with rain, snow and ice capabilities, in addition to solar exposure simulators. Icing capability, in particular, has been a critical component in wind tunnels for decades, because ice buildup on airplane surfaces can be disastrous, causing a plane to crash. Icing tunnels have refrigeration systems that cool the air and then spray fine droplets of water into the airflow, producing a glaze on the test models.

Engineers can then tinker with solutions to counter ice buildup, for example, by installing heating systems that warm the surfaces of the plane. There are a lot of other tunnel types designed for specific purposes. Some designs skip poles or wires for securing the model and instead use powerful magnets that suspend metallic models in the test section. Others provide remote control wires that let scientists actually "fly" a model plane within the test area.

The University of Texas at Arlington's Aerodynamics Research Center has what's called an arc jet tunnel, which generates supersonic streams of very hot gas at temperatures up to 8, degrees Fahrenheit 4, Celsius. These kinds of temperatures are especially useful for NASA, which subjects its spacecraft to high heat as they re-enter Earth's atmosphere.

Some tunnels omit air entirely and instead use water. Water flows much like air, but it has greater density than air and is more visible, too.

Those properties help scientists visualize flow patterns around submarines and ship hulls, or even better see shockwaves created by very fast aircraft and missiles. So what's the point of blowing all of this hot and cool air around, anyway?

It's not just so that scientists can get their geek on -- on the next page, you'll see how wind tunnels help us do a lot more than fly. Vertical wind tunnels or VWTs prove that wind tunnels aren't just for work.

VWTs let people skydive indoors also called bodyflying , a good way for novices and pros alike to learn how to skydive safely and have a blast at the same time.

Engineers and manufacturing specialists use wind tunnels to improve not just airplanes and spacecraft, but an entire assortment of industrial and consumer products. Automobile makers, in particular, rely heavily on wind tunnels. Wind tunnel tests verify engineers' calculations and identify areas for improvement in their designs.

In the case of aircraft, the tests help engineers improve aerodynamic performance — reducing drag and increasing lift — while ensuring the aircraft will be stable and controllable. Acoustic engineers use wind tunnels to measure the sound vehicles generate as they move through air.

Test findings help them to validate predictions and refine designs, which ultimately yields quieter aircraft and a better experience for passengers. Boom will begin wind tunnel testing for Overture in late During multiple rounds of testing, the engineering team will test Overture models in five wind tunnels, located in Europe and the U. Testing will range from low-speed airframe acoustics to high-speed aerodynamics. Browse press releases and download images, video content, and other assets.

Subscribe to FlyBy for Boom news and insights straight to your inbox. Update your browser to view this website correctly. Update my browser now. Aug 10, What Is Wind Tunnel Testing? From speed skaters to spacecraft, engineers use wind tunnel tests to design for optimal aerodynamics and performance. From speed skaters to spacecraft, engineers use wind tunnel tests to design for optimal aerodynamics and performance Wind tunnel testing may harness the power of new technologies, but the concept of testing air flow is hundreds of years old.

Photo credit: U. An XB lifting body model is being prepared for a wind tunnel test under a joint U. The purpose of the test is to generate data for comparison with flight data obtained at Edwards Air Force Base in California. Photo credit: National Archives What were the first wind tunnels? How do wind tunnels work? Photographer Phil Tarver captured this iconic image in Photo by Phil Tarver.