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Wind tunnels have been around for well over 100 years.

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Now, even before powered flight had been achieved, aircraft designers like the Wright Brothers

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used them to understand how air flowed over aircraft surfaces.

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Wind tunnels come in many different sizes and can reach speeds from 1 mile per hour

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to over 17,000 miles per hour.

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Most are used for testing aircraft, but they've also been used for testing things like cars,

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submarines, buildings, golf balls, and even wheelchairs.

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Wind tunnels are fairly simple devices, but have you ever wondered how one works?

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For some answers, I spoke with NASA Langley researcher Luther Jenkins to find out more.

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Well, a wind tunnel is actually a simulator.

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It allows us to simulate the conditions that an airplane or some other type of vehicle

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is actually going to experience as it's operating.

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So instead of building a full-size aircraft or a full-size car,

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we actually build a small-scale model, testing the wind tunnel to see how it's going to perform.

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And once we see that it has the performance characteristics that we desire,

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then you may take it and start manufacturing it on a mass scale.

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Anything that's going to be exposed to the air or has to travel through the air

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can actually be tested in the wind tunnel to see how it will perform.

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Earlier, you mentioned that wind tunnels come in different sizes, correct?

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That's true.

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Great. So how does that work? What, the bigger the fan, the faster the speed?

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Wind tunnels come in all shapes and sizes, but they're actually just two types of tunnels.

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One is an open-return wind tunnel, and the other one is a closed-return.

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And what it describes is the way the air flows through.

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In an open-return wind tunnel, the inlet, or the opening to the tunnel,

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is open to the atmosphere or the environment,

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and the exit, or where the air comes out, is open to the environment.

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In between, what you have is your test section, where you actually put your model, your test article.

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And then you have a diffuser, which actually causes the air to slow down a little bit before it hits the fan.

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And then the fan is downstream, so it actually pulls the air or draws the air through the tunnel like a vacuum cleaner.

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And then in your closed-return tunnels, those are a little bit more complicated

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because the air flows continuously around the loop.

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You have to have turning vanes in the corners to actually turn the air so it moves through nice and smoothly.

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You have a fan, which is actually providing the air that goes through the tunnel.

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And then you have your test section, just like in the open-return wind tunnel,

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where you would place your model.

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Now, all tunnels don't have fans.

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Some use just air sources.

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I mean, you can hook an air bottle up to the tunnel and turn it on, and the air flows through the tunnel.

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Is air the only media that you can use in a wind tunnel?

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No, actually, wind tunnels use a variety of media.

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You can use air, you can use water, you can use nitrogen, you can use freon, you can use helium.

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And all of these different gases are used to actually produce certain conditions

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that the design or the aircraft is going to actually see when it flies.

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All right, so why do we still need wind tunnels?

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I mean, can't computers today do the simulation?

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Well, computers can be used to do a lot of the simulation work.

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But just like the Wright brothers, they would start off doing testing in the wind tunnel,

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and they had to do it over and over and over again until they arrived at the final design.

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Whereas now, a lot of that work could be done on the computer,

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but you would still, once you come up with your final design, you want to test it in the wind tunnel

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just to make sure that all of the things that you predicted with the computer occur in reality.

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Sure.

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A wind tunnel is a valuable tool for an engineer.

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Every plane that flies, every car that travels along the road, every bus, every ship,

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it's tested in a wind tunnel to make sure it's going to perform as designed.

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And in that regard, we save time, we save money, and we also save a lot of lives.

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So remember, the next time you ride in a plane, a car, or even hit a golf ball,

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it was probably tested in a wind tunnel first.

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I sure wish I had a wind tunnel behind me now.

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Perfect.