The first chunk of aero analysis tools we’re going to look at is the 2D ones.
This is for two reasons: one, there aren’t many of them so we might as well get them out of the way up front. But the better reason is because knowing 2D tools’ strengths and limitations will help us better understand and talk about 3D tools later.
2D tools are exactly as you might expect: they only simulate airflow over a shape in two dimensions. A good way to visualize this is if you had a long, rectangular wing moving through the air, and were somehow able to slice it precisely in half and look at the airflow around just that 2D slice.
Because you’re not getting any of the effects of a three-dimensional wing (i.e., no influence of the air flowing up and around the wingtips) you’re seeing the most “pure” aerodynamics for that specific airfoil.
Since they only use a 2D cross-section, these tools are almost exclusively for analyzing airfoils. You can get a bit creative with what you consider an airfoil; for example, you could run the fuselage shape of a blended-wing-body and probably get a decent rough estimate of its aerodynamics.
The tools make up for this limitation by allowing a user to run both inviscid and viscous flow simulations. Viscous flow in 3D is complex and computationally expensive. In 2D though? You can run a full angle of attack sweep in less than a minute and see exactly where and how your airfoil stalls. This makes 2D tools a truly fantastic complement to every other tool you might use.
There are a lot of ways to take advantage of this capability:
- You can run airfoils at a range of Reynolds numbers and get data on how lift and drag curves change with airspeed. This helps in selecting the right airfoil for your application, as well as better modeling it in a sim environment to help tune your autopilot.
- You can add a flap to your airfoil and see how this changes lift, drag, and stall behavior. This is useful for designing actual flaps, but you can also simulate a control surface and see if, say, your elevator loses effectiveness at a high angle of attack.
- You can get hinge moment estimates from adding a flap too, which inform how strong of servos you’ll need to actually move those surfaces.
And that’s just the use cases I came up with off the top of my head!