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The design of airfoils was predicated by the study of flow around a cylinder.

Experimental evidence shows that you can calculate the flow field of an airfoil if it satisfies certain conditions, the so called Kutta condition. IE having a smooth leading edge and a sharp trailing edge.

This is because you can take a cylinder and apply a mathematical transformation, called the Kutta-Jukowski theorem, and get the estimated flow around an airfoil that satisfies the so called Kutta condition. Perhaps it's a bit of a cosmic joke that the trailing edge must be sharp and Kutta da wind in order for the condition to hold.

Anyway, what does this tell us in plain English anyone can understand? It shows us that the vortices that form at the wing tips of an airfoil are merely part of a larger 3 dimensional vortex. This vortex envelops the entire airfoil.

Experiments hint that this is actually true, for instance if you cut a vortex ring with an airfoil just right, you see it creates upwash at the leading edge of the airfoil, hinting at global circulation, as if it were a cylinder.

https://youtu.be/NF4cf8XFV8k?t=36

More rambling incoming.

The design of airfoils was predicated by the study of flow around a cylinder. Experimental evidence shows that you can calculate the flow field of an airfoil if it satisfies certain conditions, the so called Kutta condition. IE having a smooth leading edge and a sharp trailing edge. This is because you can take a cylinder and apply a mathematical transformation, called the Kutta-Jukowski theorem, and get the estimated flow around an airfoil that satisfies the so called Kutta condition. Perhaps it's a bit of a cosmic joke that the trailing edge must be sharp and Kutta da wind in order for the condition to hold. Anyway, what does this tell us in plain English anyone can understand? It shows us that the vortices that form at the wing tips of an airfoil are merely part of a larger 3 dimensional vortex. This vortex envelops the entire airfoil. Experiments hint that this is actually true, for instance if you cut a vortex ring with an airfoil just right, you see it creates upwash at the leading edge of the airfoil, hinting at global circulation, as if it were a cylinder. https://youtu.be/NF4cf8XFV8k?t=36 More rambling incoming.

(post is archived)

[–] • 1 pt

Good shit. I actually know what you're talking about. A lot to be still learned in fluid dynamics

[–] • 1 pt

The early NACA airfoil shapes were derived from two-dimensional drawings and all calculations being done on two dimensions extruded out to three. Initial Wing foils contain the same foil shape from root to tip. Later as they got more advanced they realize they could do a lot to help stability of an aircraft by changing the airfoil from the root to the tip of the aircraft. In particular they found if they used a higher lift airfoil at the tips of the wings then they could retain control when the root of the airfoil stalled. Now they've gone to almost a four-dimensional analysis where they look not only changing the airfoil from route to tip but also doing some three-dimensional piles on the front of an airfoil. This was discovered after the piles or nubs on the front of a whale's fence were understood to actually cause areas of faster and slower AirSpeed over the foil as those nubs channeled incoming air to certain areas over the foil. This greatly decreased stall speed for the airfoils. there's still a lot of improvements that can be made to airfoils. No one is looking at the electrostatic effects of dry air over non-conducting foils which are increasingly becoming more common such as carbon fiber and other things. If done right you can section an airfoil between conductivity and non-conductive sections to actually have the air create certain areas of huge electricity charge which can create a lot of forces on its own. Remember a simple dry air flowing over a non-conductive surface of the right type can create a huge electrostatic charge on that surface.

[–] • 0 pt

I've always believed in using dielectric barrier discharge as a means of flow control.

[–] • 1 pt

O e of the least recognized phenomenon associated with airflow is the electrostatic charges and the forces that can build up which under the right circumstances can control airflow and provide additional or substraction of lift.

This is dependent upon conductivity of the airfoil, dryness of the air etc.

[–] • 0 pt

That I never even thought of, thanks man. It makes sense too just the thought of dust being swirled around by a vortex makes me think of electric charges. Have you seen on some hurricanes, there are concentric rings just like an electric discharge.