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)