Wind tunnels are basically huge tubes with air blowing inside. The purpose of these tunnels is to duplicate the actions of things in flight. Researchers and engineers use wind tunnels to find about the flight of an aircraft practically. These tunnels are used by NASA to test scale and examine the models of several spacecraft and aircraft. Some tubes are huge enough to include full-size versions of aircraft and other vehicles. The air around the object is moved by the wind tunnel so that it seems like the object is flying. It creates a miniature real-life flying scenario.
The invention of Wind tunnels
When the Wright brothers invented the airplane in December 1903. They studied aerodynamics and perfected the design of their airplane’s wings. They carried out most of their tests outdoors with significant risk. But, at the present day, such testing is conducted indoors with reduced risk factors, all because of the great innovation of the self-taught British aeronautical engineer Frank Wenham (1824–1908).
He invented the modern-day wind tunnel in 1871. Originally, Wenham designed a trunk 18 inches [46cm] square and 12 feet [3.7m] long, to direct the air current horizontally. The air that flowed inside this tube had a speed of about 64km/h (40mph). Today, the world’s largest wind tunnel owned by NASA (in NASA Ames Research Center) is over 100 times longer i.e., 430m or 1400ft long, and the test section has an total area of 24m × 37m (80ft × 120 ft). This tunnel generates winds with a speed of 185km/h (115mph). This invention of Wenham has revolutionized modern day aerodynamics.
Why do we need a wind tunnel?
Wind tunnels help design planes/spacecraft that can fly swiftly, efficiently, and economically by making air move smoothly past the wings of the aircraft and their tube-like bodies. These tunnels help in studying the science of aerodynamics. Once an aircraft is up in the air, it is not easy to see how air is flowing past it. If there is any kind of design defect present in the aircraft, it won’t be able to the air at all or start dis-functioning midway. That is why every airplane and spacecraft must be tested/evaluated on the ground in a wind tunnel to avoid any form of disaster.
How Does a Wind Tunnel Work?
Generally, wind tunnels use powerful fans to move large amounts of air through the tube. The test object is securely fastened in the tunnel so that it remains stationary. The tunnel behaves like a huge pipe, which wraps itself around with a fan in the center. When the fan is switched, air blows around the pipe. This pipe has an uneven width i.e., it is narrower in some places and broader in others. The narrow region of the tube speeds up the air due to more pressure. This high speed is necessary while testing aircraft.
Testing supersonic airplanes require a speed that is five times that of a hurricane, and for testing a space shuttle, the required speed is around ten times more.
What are objects that can be tested in a wind tunnel?
The test object can be a miniature model of a vehicle/spacecraft or a part of the spacecraft. In some cases, if the tunnel is large enough, then the test object can also be a full-size aircraft or spacecraft. Common objects like tennis balls can also be used. The air flowing around the still object depicts what might happen if the object moves across the sky.
Movement of the air around an object can be evaluated in various ways. Often, smoke or dye is in the air inside the tube so that it’s movement can be observed. At times threads are attached to the object to determine air movement. Specialized instruments are used to measure/analyze the force of the air and pressure on the test object.
Parts of a wind tunnel
- A wind tunnel generally has the following working parts:
- Drive motors: Drive motors are large electric motors that help in spinning the fan.
- Supersonic, high-speed test section: The section where the model test aircraft is placed.
- Vanes: Vanes are airfoils located in the corners that help turn the airflow through 90 degrees without experiencing energy loss.
- Compressor: The giant fans that help in generating the high-speed wind.
- Acoustic muffler: Acoustic mufflers help limit the noise produced by the fans and simulate a realistic airflow accurately.
- Access doors: The doors allow the researchers to get in the tunnel without altering the interior arrangement.
- Subsonic, low-speed test section: The smaller test section where the air blows comparatively slower.
- Air dryer: Air dryers help in removing moisture from the airflow.
Wind tunnels are generally acknowledged for being utilized in testing/evaluating new aircraft and space shuttles i.e., vehicles that theoretically travel in a static air stream. These tunnels can also be used in an alternative way, like simulating the effect of fast-moving winds on stationery structures, such as skyscrapers, giant statues, and bridges.
Architects and engineers observe and examine the loads that high-speed winds impose on these structures and how it varies with different designs. It also helps in determining how skyscrapers affect the blowing winds and push it down to ground level.
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