What are wind tunnels used for?
Assuming you’ve just built a huge new airliner, now it’s time for a real test. Even if you spend millions of dollars designing a plane made of shiny titanium metal and test it on the tarmac to see if it actually flies, your calculations can go wrong.
For example, the plane takes off and after twenty seconds it falls and lands on a city full of 5 million people. This is probably not the most efficient way to try something so risky. That’s why aircraft designers first test these things on the ground using scale models in wind tunnels. Here’s a closer look at how they work.
based on science
To build planes that fly fast, efficiently, and economically, designers must ensure that air flows smoothly over their wings and past their tube-shaped bodies. This is the science of aerodynamics. By the time a plane is airborne, it would be difficult to know what air is passing by (but a skilled test pilot will know the cause of any problems).
In case there is something wrong with your design, the plane will not fly at all. For this reason, modern aircraft and spacecraft are tested on the ground in a wind tunnel, which is a pipe-like structure through which air is blown at very high speeds.
The logic behind the wind tunnel is clear and simple: when a plane can’t move through the air, perhaps the air can move past the plane. From a scientific point of view, it is the same. When the plane drags (causing air resistance) as it rises through the sky, the air will drag in exactly the same way as it shoots past a stationary model plane on the ground.
Nothing can stop someone from creating a huge wind tunnel and testing a full-size model, and certainly NASA, the US space agency, has such structures. However, it is often much cheaper to use a smaller scale model aircraft in a smaller wind tunnel as well.
How does a wind tunnel work?
A wind tunnel looks a lot like a big tube that winds around and around and has a fan in the middle. When the fan is turned on, the air blows around the pipe in a circle. It is best to include a small door to enter plus a test room in the middle and voila, a wind tunnel is created.
Essentially, it is quite a bit more sophisticated than that. Instead of having a uniform shape all around, the pipe is narrower in some places and wider in others. Air needs to speed up to get through narrow pipes. When the pipe is narrower, the air has to go faster.
Similar to a bicycle pump, when the air comes out through the narrow nozzle, it speeds up. It is also similar to a wind valley, in that the wind blows much stronger, concentrated by the hills on either side.
A wind tunnel that has narrow sections makes it easy to increase speed, which is very necessary. Testing a supersonic aircraft requires wind speeds five times faster than a hurricane. When it comes to testing a space shuttle, this requires a wind ten times faster. Some kind of wind!