In a couple of weeks here I’m going to be supporting a wind tunnel test for a client. So, because that’s where my mind is, I’m going to talk about this aspect of aero engineering.
I love wind tunnels and wind tunnel testing. I think they’re awesome, and I want you to think so too.
Not just because I’m biased from working in one in undergrad (though I definitely am biased by that experience). Or because the facilities are genuinely incredible marvels of human ingenuity and engineering.
They’re awesome because wind tunnel testing is the best way to get your first true evaluation of the aerodynamics, and therefore behavior and performance, of any air vehicle.
You can do as much simulation and analysis as you want, but you don’t know the truth about your airplane until it’s flying through the air. And completing a wind tunnel test is a much safer and more controlled way to get that data than going straight to flight test.
This means that understanding how a wind tunnel test campaign fits into any aircraft’s development cycle, and the dividends you get from that investment, is valuable to anyone in the aero industry. And that’s why we’re here.
Before we get into the technical bits though, let me get a handful of misconceptions out of the way:
- When I talk about “wind tunnels” I don’t mean the indoor skydiving places. Those are very different from what I’m talking about here—for one, most wind tunnel facilities blow the air horizontally, not vertically.
- Despite what car commercials would have you believe, we don’t use wind tunnels exclusively to blow trails of smoke over vehicles and then go “ah yes, this car is quite aerodynamic!” Flow visualization techniques are very useful, but they’re not the primary output from a test.
- No, wind tunnels are not going to be entirely replaced by CFD (computational fluid dynamics) simulations. I’m of the strong opinion that, no matter how accurate or fast or detailed those simulations become, there is no replacement for testing a physical object in actual airflow.
Now that we’ve cleared the air (pun not intended), let’s get into the details of what a wind tunnel really is, and why I love them so much.