This seems to be a teaching aid to "pen and paper" aerodynamics. If you want simulation, i.e. CFD, you need a program like OpenFOAM. Be warned, though, the learning curve is steep - especially if you don't have any background. It will go wrong often and you won't know why.

> Or is there a better open source program?

XFLR 5. A nice graphical UI using XFOIL for 2D section CFD and basic algorithms for 3D flow analysis too.

http://www.xflr5.tech/xflr5.htm

This is the aerodynamics they teach you first as an undergraduate. It is not nonsense, but there are better methods out there. It might be good for your use case, it might not. Comes down to what you’re trying to accomplish.

Other solutions I am aware of have steep learning curves, so maybe give it a try.

You'll see if you dig into it that it only does 2D. You could extend it to 3D with some serious work, and for simple geometries at low angles of attack and high Reynolds Number it will probably do fine.

But if you want better fidelity the best open-source CFD suite I'm familiar with is OpenFOAM. Unfortunately you have to have an adequate understanding of the math/physics to use that as OpenFOAM doesn't hold your hand even a little bit. There's really not much of a market at all for "casual flow modeling".